diff --git a/core/includes/theme.inc b/core/includes/theme.inc
index 6cd1712..d139476 100644
--- a/core/includes/theme.inc
+++ b/core/includes/theme.inc
@@ -667,6 +667,8 @@ function theme($hook, $variables = array()) {
   }
 
   // Send prepare arguments to invoke hooks with $variables passed by reference.
+  // @todo Change this to hook_menu() style where you need to return $variables
+  //   instead of altering by reference.
   $prepare_args = array(&$variables, $base_theme_hook);
 
   // Invokes hook_theme_prepare(), hook_theme_prepare_THEME_HOOK() for enabled
@@ -680,14 +682,6 @@ function theme($hook, $variables = array()) {
     }
   }
 
-  // Invokes hook_theme_prepare(), hook_theme_prepare_THEME_HOOK() for the active
-  // theme, which takes precedence over modules.
-  // @todo Replace with Drupal::themeHandler()->invoke() once implemented.
-  // @see https://drupal.org/node/2029819
-  foreach ($prepare_hooks as $prepare_hook) {
-    theme_invoke($prepare_hook, $prepare_args);
-  }
-
   // Invokes hook_preprocess() and hook_preprocess_HOOK() implementations. This
   // phase is deprecated and is run in between hook_theme_prepare[_THEME_HOOK]()
   // and hook_theme_prepare[_THEME_HOOK]_alter().
@@ -701,8 +695,6 @@ function theme($hook, $variables = array()) {
 
   // Invokes hook_theme_prepare_alter(), hook_theme_prepare_THEME_ID_alter()
   // for enabled modules.
-  // @todo Add Drupal::themeHandler()->alter() invocations once implemented.
-  // @see https://drupal.org/node/2029819
   foreach ($prepare_hooks as $prepare_hook) {
     Drupal::moduleHandler()->alter($prepare_hook, $variables, $base_theme_hook);
   }
@@ -1139,39 +1131,6 @@ function theme_disable($theme_list) {
 }
 
 /**
- * Rudimentary and temporary method for invoking theme hooks.
- *
- * @param string $hook
- *   The hook name to invoke.
- * @param array $args
- *   The array of arguments to pass to hook invocation (by reference).
- *
- * @return mixed
- *   The value returned varies on which hook is invoked.
- *
- * @todo Remove once a proper Drupal::themeHandler() is created.
- * @see https://drupal.org/node/2029819
- */
-function theme_invoke($hook, &$args = array()) {
-  // Allow the active theme to invoke hooks after the theme system has been
-  // initialized.
-  global $theme, $base_theme_info;
-  if (isset($theme)) {
-    $theme_keys = array();
-    foreach ($base_theme_info as $base) {
-      $theme_keys[] = $base->name;
-    }
-    $theme_keys[] = $theme;
-    foreach ($theme_keys as $theme_key) {
-      $function = $theme_key . '_' . $hook;
-      if (function_exists($function)) {
-        call_user_func_array($function, $args);
-      }
-    }
-  }
-}
-
-/**
  * @addtogroup themeable
  * @{
  */
diff --git a/core/modules/system/lib/Drupal/system/Tests/Theme/ThemePrepareTest.php b/core/modules/system/lib/Drupal/system/Tests/Theme/ThemePrepareTest.php
index 5ca1d0f..fa6c486 100644
--- a/core/modules/system/lib/Drupal/system/Tests/Theme/ThemePrepareTest.php
+++ b/core/modules/system/lib/Drupal/system/Tests/Theme/ThemePrepareTest.php
@@ -44,31 +44,22 @@ public function testThemePrepare() {
     $this->drupalGet('theme-test/prepare');
 
     $this->assertRaw('<p>moduleVariable1: Drupal\theme_test\ThemeTestController::prepare<br>
-test_theme_theme_prepare<br>
-test_theme_theme_prepare_theme_test_prepare<br>
 theme_test_theme_prepare_alter<br>
 test_theme_theme_prepare_alter<br>
 test_theme_theme_prepare_theme_test_prepare_alter</p>');
 
     $this->assertRaw('<p>moduleVariable2: Drupal\theme_test\ThemeTestController::prepare<br>
-test_theme_theme_prepare<br>
-test_theme_theme_prepare_theme_test_prepare<br>
 theme_test_theme_prepare_alter<br>
 test_theme_theme_prepare_alter<br>
 test_theme_theme_prepare_theme_test_prepare_alter</p>');
 
     $this->assertRaw('<p>moduleVariableSuggestion1: Drupal\theme_test\ThemeTestController::prepare<br>
-test_theme_theme_prepare<br>
-test_theme_theme_prepare_theme_test_prepare<br>
 theme_test_theme_prepare_alter<br>
 test_theme_theme_prepare_alter<br>
 test_theme_theme_prepare_theme_test_prepare_alter</p>');
 
     $this->assertRaw('<p>moduleVariableSuggestion2: Drupal\theme_test\ThemeTestController::prepare<br>
 theme_test_theme_prepare_theme_test_prepare__implemented<br>
-test_theme_theme_prepare<br>
-test_theme_theme_prepare_theme_test_prepare<br>
-test_theme_theme_prepare_theme_test_prepare__implemented<br>
 theme_test_theme_prepare_alter<br>
 test_theme_theme_prepare_alter<br>
 test_theme_theme_prepare_theme_test_prepare_alter<br>
@@ -77,9 +68,6 @@ public function testThemePrepare() {
 
     $this->assertRaw('<p>moduleVariableSuggestion3: Drupal\theme_test\ThemeTestController::prepare<br>
 theme_test_theme_prepare_theme_test_prepare__implemented__extended<br>
-test_theme_theme_prepare<br>
-test_theme_theme_prepare_theme_test_prepare<br>
-test_theme_theme_prepare_theme_test_prepare__implemented__extended<br>
 theme_test_theme_prepare_alter<br>
 test_theme_theme_prepare_alter<br>
 test_theme_theme_prepare_theme_test_prepare_alter<br>
@@ -87,141 +75,41 @@ public function testThemePrepare() {
 test_theme_theme_prepare_theme_test_prepare__implemented__extended_alter</p>');
 
     $this->assertRaw('<p>moduleElement1: Drupal\theme_test\ThemeTestController::prepare<br>
-test_theme_theme_prepare<br>
-test_theme_theme_prepare_theme_test_prepare<br>
 theme_test_theme_prepare_alter<br>
 test_theme_theme_prepare_alter<br>
 test_theme_theme_prepare_theme_test_prepare_alter</p>');
 
-    $this->assertRaw('<p>moduleInjectedVariable1: theme_test_theme_prepare<br>
-test_theme_theme_prepare<br>
-test_theme_theme_prepare_theme_test_prepare<br>
+    $this->assertRaw('<p>moduleInjectedVariable1: Variable added in: theme_test_theme_prepare<br>
 theme_test_theme_prepare_alter<br>
 test_theme_theme_prepare_alter<br>
 test_theme_theme_prepare_theme_test_prepare_alter</p>');
 
-    $this->assertRaw('<p>moduleInjectedVariable2: theme_test_theme_prepare_theme_test_prepare_element<br>
-test_theme_theme_prepare<br>
-test_theme_theme_prepare_theme_test_prepare<br>
+    $this->assertRaw('<p>moduleInjectedVariable2: Variable added in: theme_test_theme_prepare_theme_test_prepare_element<br>
 theme_test_theme_prepare_alter<br>
 test_theme_theme_prepare_alter<br>
 test_theme_theme_prepare_theme_test_prepare_alter</p>');
 
-    $this->assertRaw('<p>themeInjectedVariable1: test_theme_theme_prepare<br>
-test_theme_theme_prepare<br>
-test_theme_theme_prepare_theme_test_prepare<br>
+    $this->assertRaw('<p>moduleInjectedVariable3: Variable added in: theme_test_theme_prepare_theme_test_prepare_element_alter<br>
 theme_test_theme_prepare_alter<br>
 test_theme_theme_prepare_alter<br>
 test_theme_theme_prepare_theme_test_prepare_alter</p>');
 
-    $this->assertRaw('<p>moduleInjectedVariable3: theme_test_theme_prepare_theme_test_prepare_element_alter<br>
-test_theme_theme_prepare<br>
-test_theme_theme_prepare_theme_test_prepare<br>
+    $this->assertRaw('<p>themeInjectedVariable1: Variable added in: test_theme_theme_prepare_theme_test_prepare_element_alter<br>
 theme_test_theme_prepare_alter<br>
 test_theme_theme_prepare_alter<br>
 test_theme_theme_prepare_theme_test_prepare_alter</p>');
 
     $this->assertRaw('<p>moduleElementSuggestion1: Drupal\theme_test\ThemeTestController::prepare<br>
-test_theme_theme_prepare<br>
-test_theme_theme_prepare_theme_test_prepare<br>
-theme_test_theme_prepare_alter<br>
-test_theme_theme_prepare_alter<br>
-test_theme_theme_prepare_theme_test_prepare_alter</p>');
-
-    $this->assertRaw('<p>moduleInjectedVariable1: theme_test_theme_prepare<br>
-test_theme_theme_prepare<br>
-test_theme_theme_prepare_theme_test_prepare<br>
-theme_test_theme_prepare_alter<br>
-test_theme_theme_prepare_alter<br>
-test_theme_theme_prepare_theme_test_prepare_alter</p>');
-
-    $this->assertRaw('<p>moduleInjectedVariable2: theme_test_theme_prepare_theme_test_prepare_element<br>
-test_theme_theme_prepare<br>
-test_theme_theme_prepare_theme_test_prepare<br>
-theme_test_theme_prepare_alter<br>
-test_theme_theme_prepare_alter<br>
-test_theme_theme_prepare_theme_test_prepare_alter</p>');
-
-    $this->assertRaw('<p>themeInjectedVariable1: test_theme_theme_prepare<br>
-test_theme_theme_prepare<br>
-test_theme_theme_prepare_theme_test_prepare<br>
-theme_test_theme_prepare_alter<br>
-test_theme_theme_prepare_alter<br>
-test_theme_theme_prepare_theme_test_prepare_alter</p>');
-
-    $this->assertRaw('<p>moduleInjectedVariable3: theme_test_theme_prepare_theme_test_prepare_element_alter<br>
-test_theme_theme_prepare<br>
-test_theme_theme_prepare_theme_test_prepare<br>
 theme_test_theme_prepare_alter<br>
 test_theme_theme_prepare_alter<br>
 test_theme_theme_prepare_theme_test_prepare_alter</p>');
 
     $this->assertRaw('<p>moduleElementSuggestion2: Drupal\theme_test\ThemeTestController::prepare<br>
-test_theme_theme_prepare<br>
-test_theme_theme_prepare_theme_test_prepare<br>
-theme_test_theme_prepare_alter<br>
-test_theme_theme_prepare_alter<br>
-test_theme_theme_prepare_theme_test_prepare_alter</p>');
-
-    $this->assertRaw('<p>moduleInjectedVariable1: theme_test_theme_prepare<br>
-test_theme_theme_prepare<br>
-test_theme_theme_prepare_theme_test_prepare<br>
-theme_test_theme_prepare_alter<br>
-test_theme_theme_prepare_alter<br>
-test_theme_theme_prepare_theme_test_prepare_alter</p>');
-
-    $this->assertRaw('<p>moduleInjectedVariable2: theme_test_theme_prepare_theme_test_prepare_element<br>
-test_theme_theme_prepare<br>
-test_theme_theme_prepare_theme_test_prepare<br>
-theme_test_theme_prepare_alter<br>
-test_theme_theme_prepare_alter<br>
-test_theme_theme_prepare_theme_test_prepare_alter</p>');
-
-    $this->assertRaw('<p>themeInjectedVariable1: test_theme_theme_prepare<br>
-test_theme_theme_prepare<br>
-test_theme_theme_prepare_theme_test_prepare<br>
-theme_test_theme_prepare_alter<br>
-test_theme_theme_prepare_alter<br>
-test_theme_theme_prepare_theme_test_prepare_alter</p>');
-
-    $this->assertRaw('<p>moduleInjectedVariable3: theme_test_theme_prepare_theme_test_prepare_element_alter<br>
-test_theme_theme_prepare<br>
-test_theme_theme_prepare_theme_test_prepare<br>
 theme_test_theme_prepare_alter<br>
 test_theme_theme_prepare_alter<br>
 test_theme_theme_prepare_theme_test_prepare_alter</p>');
 
     $this->assertRaw('<p>moduleElementSuggestion3: Drupal\theme_test\ThemeTestController::prepare<br>
-test_theme_theme_prepare<br>
-test_theme_theme_prepare_theme_test_prepare<br>
-theme_test_theme_prepare_alter<br>
-test_theme_theme_prepare_alter<br>
-test_theme_theme_prepare_theme_test_prepare_alter</p>');
-
-    $this->assertRaw('<p>moduleInjectedVariable1: theme_test_theme_prepare<br>
-test_theme_theme_prepare<br>
-test_theme_theme_prepare_theme_test_prepare<br>
-theme_test_theme_prepare_alter<br>
-test_theme_theme_prepare_alter<br>
-test_theme_theme_prepare_theme_test_prepare_alter</p>');
-
-    $this->assertRaw('<p>moduleInjectedVariable2: theme_test_theme_prepare_theme_test_prepare_element<br>
-test_theme_theme_prepare<br>
-test_theme_theme_prepare_theme_test_prepare<br>
-theme_test_theme_prepare_alter<br>
-test_theme_theme_prepare_alter<br>
-test_theme_theme_prepare_theme_test_prepare_alter</p>');
-
-    $this->assertRaw('<p>themeInjectedVariable1: test_theme_theme_prepare<br>
-test_theme_theme_prepare<br>
-test_theme_theme_prepare_theme_test_prepare<br>
-theme_test_theme_prepare_alter<br>
-test_theme_theme_prepare_alter<br>
-test_theme_theme_prepare_theme_test_prepare_alter</p>');
-
-    $this->assertRaw('<p>moduleInjectedVariable3: theme_test_theme_prepare_theme_test_prepare_element_alter<br>
-test_theme_theme_prepare<br>
-test_theme_theme_prepare_theme_test_prepare<br>
 theme_test_theme_prepare_alter<br>
 test_theme_theme_prepare_alter<br>
 test_theme_theme_prepare_theme_test_prepare_alter</p>');
@@ -237,18 +125,12 @@ function testThemePrepareSubtheme() {
     $this->drupalGet('theme-test/prepare-subtheme');
 
     $this->assertRaw('<p>subThemePrepare: Drupal\theme_test\ThemeTestController::prepareSubtheme<br>
-test_basetheme_theme_prepare_theme_test_prepare<br>
-test_subtheme_theme_prepare_theme_test_prepare<br>
 theme_test_theme_prepare_alter<br>
 test_basetheme_theme_prepare_theme_test_prepare_alter<br>
 test_subtheme_theme_prepare_theme_test_prepare_alter</p>');
 
     $this->assertRaw('<p>subThemePrepareSuggestion: Drupal\theme_test\ThemeTestController::prepareSubtheme<br>
 theme_test_theme_prepare_theme_test_prepare__implemented<br>
-test_basetheme_theme_prepare_theme_test_prepare<br>
-test_subtheme_theme_prepare_theme_test_prepare<br>
-test_basetheme_theme_prepare_theme_test_prepare__implemented<br>
-test_subtheme_theme_prepare_theme_test_prepare__implemented<br>
 theme_test_theme_prepare_alter<br>
 test_basetheme_theme_prepare_theme_test_prepare_alter<br>
 test_subtheme_theme_prepare_theme_test_prepare_alter<br>
diff --git a/core/modules/system/tests/modules/theme_test/theme_test.module b/core/modules/system/tests/modules/theme_test/theme_test.module
index dd2f508..8c300ed 100644
--- a/core/modules/system/tests/modules/theme_test/theme_test.module
+++ b/core/modules/system/tests/modules/theme_test/theme_test.module
@@ -207,7 +207,7 @@ function theme_test_theme_prepare(&$variables, $hook) {
     $variables['element']['moduleInjectedVariable1'] = array(
       '#theme' => 'theme_test_prepare__element',
       '#title' => 'moduleInjectedVariable1',
-      '#value' => __FUNCTION__,
+      '#value' => 'Variable added in: ' . __FUNCTION__,
     );
   }
 }
@@ -256,7 +256,7 @@ function theme_test_theme_prepare_theme_test_prepare_element(&$variables) {
   $variables['element']['moduleInjectedVariable2'] = array(
     '#theme' => 'theme_test_prepare__element',
     '#title' => 'moduleInjectedVariable2',
-    '#value' => __FUNCTION__,
+    '#value' => 'Variable added in: ' . __FUNCTION__,
   );
 }
 
@@ -267,6 +267,6 @@ function theme_test_theme_prepare_theme_test_prepare_element_alter(&$variables)
   $variables['element']['moduleInjectedVariable3'] = array(
     '#theme' => 'theme_test_prepare__element',
     '#title' => 'moduleInjectedVariable3',
-    '#value' => __FUNCTION__,
+    '#value' => 'Variable added in: ' . __FUNCTION__,
   );
 }
diff --git a/core/modules/system/tests/themes/test_basetheme/test_basetheme.theme b/core/modules/system/tests/themes/test_basetheme/test_basetheme.theme
index 7def511..473e289 100644
--- a/core/modules/system/tests/themes/test_basetheme/test_basetheme.theme
+++ b/core/modules/system/tests/themes/test_basetheme/test_basetheme.theme
@@ -6,13 +6,6 @@
  */
 
 /**
- * Implements hook_theme_prepare_THEME_HOOK().
- */
-function test_basetheme_theme_prepare_theme_test_prepare(&$variables) {
-  $variables['value'] .= "<br>\n" . __FUNCTION__;
-}
-
-/**
  * Implements hook_theme_prepare_THEME_HOOK_alter().
  */
 function test_basetheme_theme_prepare_theme_test_prepare_alter(&$variables) {
@@ -20,13 +13,6 @@ function test_basetheme_theme_prepare_theme_test_prepare_alter(&$variables) {
 }
 
 /**
- * Implements hook_theme_prepare_THEME_HOOK__SUGGESTION().
- */
-function test_basetheme_theme_prepare_theme_test_prepare__implemented(&$variables) {
-  $variables['value'] .= "<br>\n" . __FUNCTION__;
-}
-
-/**
  * Implements hook_theme_prepare_THEME_HOOK__SUGGESTION_alter().
  */
 function test_basetheme_theme_prepare_theme_test_prepare__implemented_alter(&$variables) {
diff --git a/core/modules/system/tests/themes/test_subtheme/test_subtheme.theme b/core/modules/system/tests/themes/test_subtheme/test_subtheme.theme
index affb5fb..6ba3eb6 100644
--- a/core/modules/system/tests/themes/test_subtheme/test_subtheme.theme
+++ b/core/modules/system/tests/themes/test_subtheme/test_subtheme.theme
@@ -6,13 +6,6 @@
  */
 
 /**
- * Implements hook_theme_prepare_THEME_HOOK().
- */
-function test_subtheme_theme_prepare_theme_test_prepare(&$variables) {
-  $variables['value'] .= "<br>\n" . __FUNCTION__;
-}
-
-/**
  * Implements hook_theme_prepare_THEME_HOOK_alter().
  */
 function test_subtheme_theme_prepare_theme_test_prepare_alter(&$variables) {
@@ -20,13 +13,6 @@ function test_subtheme_theme_prepare_theme_test_prepare_alter(&$variables) {
 }
 
 /**
- * Implements hook_theme_prepare_THEME_HOOK__SUGGESTION().
- */
-function test_subtheme_theme_prepare_theme_test_prepare__implemented(&$variables) {
-  $variables['value'] .= "<br>\n" . __FUNCTION__;
-}
-
-/**
  * Implements hook_theme_prepare_THEME_HOOK__SUGGESTION_alter().
  */
 function test_subtheme_theme_prepare_theme_test_prepare__implemented_alter(&$variables) {
diff --git a/core/modules/system/tests/themes/test_theme/test_theme.theme b/core/modules/system/tests/themes/test_theme/test_theme.theme
index 6cc73f0..01f47b9 100644
--- a/core/modules/system/tests/themes/test_theme/test_theme.theme
+++ b/core/modules/system/tests/themes/test_theme/test_theme.theme
@@ -86,22 +86,6 @@ function test_theme_theme_test_function_suggestions__module_override($variables)
 }
 
 /**
- * Implements hook_theme_prepare().
- */
-function test_theme_theme_prepare(&$variables, $hook) {
-  if ($hook === 'theme_test_prepare') {
-    $variables['value'] .= "<br>\n" . __FUNCTION__;
-  }
-  elseif ($hook === 'theme_test_prepare_element') {
-    $variables['element']['themeInjectedVariable1'] = array(
-      '#theme' => 'theme_test_prepare__element',
-      '#title' => 'themeInjectedVariable1',
-      '#value' => __FUNCTION__,
-    );
-  }
-}
-
-/**
  * Implements hook_theme_prepare_alter().
  */
 function test_theme_theme_prepare_alter(&$variables, $hook) {
@@ -111,10 +95,14 @@ function test_theme_theme_prepare_alter(&$variables, $hook) {
 }
 
 /**
- * Implements hook_theme_prepare_THEME_HOOK().
+ * Implements hook_theme_prepare_THEME_HOOK_alter().
  */
-function test_theme_theme_prepare_theme_test_prepare(&$variables) {
-  $variables['value'] .= "<br>\n" . __FUNCTION__;
+function test_theme_theme_prepare_theme_test_prepare_element_alter(&$variables) {
+  $variables['element']['themeInjectedVariable1'] = array(
+    '#theme' => 'theme_test_prepare__element',
+    '#title' => 'themeInjectedVariable1',
+    '#value' => 'Variable added in: ' . __FUNCTION__,
+  );
 }
 
 /**
@@ -125,13 +113,6 @@ function test_theme_theme_prepare_theme_test_prepare_alter(&$variables) {
 }
 
 /**
- * Implements hook_theme_prepare_THEME_HOOK__SUGGESTION().
- */
-function test_theme_theme_prepare_theme_test_prepare__implemented(&$variables) {
-  $variables['value'] .= "<br>\n" . __FUNCTION__;
-}
-
-/**
  * Implements hook_theme_prepare_THEME_HOOK__SUGGESTION_alter().
  */
 function test_theme_theme_prepare_theme_test_prepare__implemented_alter(&$variables) {
@@ -139,13 +120,6 @@ function test_theme_theme_prepare_theme_test_prepare__implemented_alter(&$variab
 }
 
 /**
- * Implements hook_theme_prepare_THEME_HOOK__SUGGESTION().
- */
-function test_theme_theme_prepare_theme_test_prepare__implemented__extended(&$variables) {
-  $variables['value'] .= "<br>\n" . __FUNCTION__;
-}
-
-/**
  * Implements hook_theme_prepare_THEME_HOOK__SUGGESTION_alter().
  */
 function test_theme_theme_prepare_theme_test_prepare__implemented__extended_alter(&$variables) {
diff --git a/core/modules/system/theme.api.php b/core/modules/system/theme.api.php
index eff8315..10c7d61 100644
--- a/core/modules/system/theme.api.php
+++ b/core/modules/system/theme.api.php
@@ -172,7 +172,7 @@ function hook_preprocess_HOOK(&$variables) {
 /**
  * Prepares variables for theme functions and templates.
  *
- * This hook allows any module or theme to prepare variables for any theme hook.
+ * This hook allows any module to prepare variables for any theme hook.
  * hook_theme_prepare_THEME_HOOK() can be used to prepare variables for a
  * specific theme hook.
  *
@@ -250,8 +250,8 @@ function hook_theme_prepare_alter(&$variables, $hook) {
 /**
  * Prepares variables for a specific theme hook or theme hook suggestion.
  *
- * This hook allow any module or theme to prepare theme variables for a specific
- * theme hook or theme hook suggestion.
+ * This hook allows any module to prepare theme variables for a specific theme
+ * hook or theme hook suggestion.
  *
  * THEME_HOOK can be either the base theme hook or a more specific suggestion
  * using the double-underscore ('__') notation.
@@ -261,7 +261,6 @@ function hook_theme_prepare_alter(&$variables, $hook) {
  * @param array $variables
  *   The associative array of variables, passed by reference (modify in place).
  *
- * @see rdf_preprocess_image()
  * @see hook_theme_prepare_THEME_HOOK_alter()
  * @see hook_theme_prepare_alter()
  * @see hook_theme_prepare()