diff --git a/core/includes/bootstrap.inc b/core/includes/bootstrap.inc
index 1a06544..afe2bda 100644
--- a/core/includes/bootstrap.inc
+++ b/core/includes/bootstrap.inc
@@ -2340,8 +2340,7 @@ function _drupal_bootstrap_page_cache() {
   }
   else {
     drupal_bootstrap(DRUPAL_BOOTSTRAP_VARIABLES, FALSE);
-    $config = config('system.performance');
-    $cache_enabled = $config->get('cache');
+    $cache_enabled = config('system.performance')->get('cache');
   }
   drupal_block_denied(ip_address());
   // If there is no session cookie and cache is enabled (or forced), try
diff --git a/core/includes/common.inc b/core/includes/common.inc
index 3a79f0e..bc748a9 100644
--- a/core/includes/common.inc
+++ b/core/includes/common.inc
@@ -2597,8 +2597,7 @@ function drupal_page_footer() {
   // Commit the user session, if needed.
   drupal_session_commit();
 
-  $config = config('system.performance');
-  if ($config->get('cache') && ($cache = drupal_page_set_cache())) {
+  if (config('system.performance')->get('cache') && ($cache = drupal_page_set_cache())) {
     drupal_serve_page_from_cache($cache);
   }
   else {
diff --git a/core/includes/form.inc b/core/includes/form.inc
index 1c3841f..9390e2b 100644
--- a/core/includes/form.inc
+++ b/core/includes/form.inc
@@ -856,8 +856,7 @@ function drupal_process_form($form_id, &$form, &$form_state) {
       // We'll clear out the cached copies of the form and its stored data
       // here, as we've finished with them. The in-memory copies are still
       // here, though.
-      $config = config('system.performance');
-      if (!$config->get('cache') && !empty($form_state['values']['form_build_id'])) {
+      if (!config('system.performance')->get('cache') && !empty($form_state['values']['form_build_id'])) {
         cache('form')->delete('form_' . $form_state['values']['form_build_id']);
         cache('form')->delete('form_state_' . $form_state['values']['form_build_id']);
       }
diff --git a/core/includes/install.core.inc b/core/includes/install.core.inc
index f0b969f..a814e84 100644
--- a/core/includes/install.core.inc
+++ b/core/includes/install.core.inc
@@ -1012,8 +1012,7 @@ function install_settings_form_submit($form, &$form_state) {
     // How best to handle errors here?
   };
 
-  // Write out a .htaccess file that will protect the config directory from
-  // prying eyes.
+  // Add a .htaccess file to protect the config directory from prying eyes.
   file_save_htaccess($config_path, TRUE);
 
   // Indicate that the settings file has been verified, and check the database
diff --git a/core/includes/language.inc b/core/includes/language.inc
index d1cc818..94848c2 100644
--- a/core/includes/language.inc
+++ b/core/includes/language.inc
@@ -343,8 +343,7 @@ function language_provider_invoke($provider_id, $provider = NULL) {
 
     // If the language provider has no cache preference or this is satisfied
     // we can execute the callback.
-    $config = config('system.performance');
-    $cache = !isset($provider['cache']) || $user->uid || $provider['cache'] == $config->get('cache');
+    $cache = !isset($provider['cache']) || $user->uid || $provider['cache'] == config('system.performance')->get('cache');
     $callback = isset($provider['callbacks']['language']) ? $provider['callbacks']['language'] : FALSE;
     $langcode = $cache && function_exists($callback) ? $callback($languages) : FALSE;
     $results[$provider_id] = isset($languages[$langcode]) ? $languages[$langcode] : FALSE;
diff --git a/core/lib/Drupal/Core/Cache/DatabaseBackend.php b/core/lib/Drupal/Core/Cache/DatabaseBackend.php
index 7afd698..b2a4d6a 100644
--- a/core/lib/Drupal/Core/Cache/DatabaseBackend.php
+++ b/core/lib/Drupal/Core/Cache/DatabaseBackend.php
@@ -101,8 +101,7 @@ class DatabaseBackend implements CacheBackendInterface {
     // timer. The cache variable is loaded into the $user object by
     // _drupal_session_read() in session.inc. If the data is permanent or we're
     // not enforcing a minimum cache lifetime always return the cached data.
-    $config = config('system.performance');
-    if ($cache->expire != CACHE_PERMANENT && $config->get('cache_lifetime') && $user->cache > $cache->created) {
+    if ($cache->expire != CACHE_PERMANENT && config('system.performance')->get('cache_lifetime') && $user->cache > $cache->created) {
       // This cache data is too old and thus not valid for us, ignore it.
       return FALSE;
     }
diff --git a/core/lib/Drupal/Core/Config/DrupalConfig.php b/core/lib/Drupal/Core/Config/DrupalConfig.php
index eb4757f..44d009c 100644
--- a/core/lib/Drupal/Core/Config/DrupalConfig.php
+++ b/core/lib/Drupal/Core/Config/DrupalConfig.php
@@ -123,6 +123,7 @@ class DrupalConfig {
     else {
       drupal_array_set_nested_value($this->data, $parts, $value);
     }
+    return $this;
   }
 
   public function castValue($value) {
diff --git a/core/modules/color/color.test b/core/modules/color/color.test
index 616d19a..0398f26 100644
--- a/core/modules/color/color.test
+++ b/core/modules/color/color.test
@@ -93,8 +93,7 @@ class ColorTestCase extends DrupalWebTestCase {
 
     // Test with aggregated CSS turned on.
     $config = config('system.performance');
-    $config->set('preprocess_css', 1);
-    $config->save();
+    $config->set('preprocess_css', 1)->save();
     $this->drupalGet('<front>');
     $stylesheets = variable_get('drupal_css_cache_files', array());
     $stylesheet_content = '';
@@ -102,8 +101,7 @@ class ColorTestCase extends DrupalWebTestCase {
       $stylesheet_content .= join("\n", file(drupal_realpath($uri)));
     }
     $this->assertTrue(strpos($stylesheet_content, 'public://') === FALSE, 'Make sure the color paths have been translated to local paths. (' . $theme . ')');
-    $config->set('preprocess_css', 0);
-    $config->save();
+    $config->set('preprocess_css', 0)->save();
   }
 
   /**
diff --git a/core/modules/config/config.test b/core/modules/config/config.test
index d97eff1..ccbf4ad 100644
--- a/core/modules/config/config.test
+++ b/core/modules/config/config.test
@@ -147,11 +147,12 @@ class ConfigFileContentTestCase extends DrupalWebTestCase {
     $this->assertIdentical($db_config, FALSE);
     $this->assertFalse(file_exists($config_dir . '/' . $name . '.' . $this->fileExtension));
 
+    // Chainable ->set()->save()
     // Attempt to delete non-existing configuration.
     // Write and read an array value.
     // Add an array value to a nested key.
-    // Type casting into string.
+    // Type casting into string. (recursively)
     // NULL value behavior.
-    // List config names by prefix.
+    // List config names by prefix. (and without prefix)
   }
 }
diff --git a/core/modules/poll/poll.test b/core/modules/poll/poll.test
index adec664..c0a51d2 100644
--- a/core/modules/poll/poll.test
+++ b/core/modules/poll/poll.test
@@ -496,9 +496,7 @@ class PollVoteCheckHostname extends PollTestCase {
 
     // Enable page cache to verify that the result page is not saved in the
     // cache when anonymous voting is allowed.
-    $config = config('system.performance');
-    $config->set('cache', 1);
-    $config->save();
+    config('system.performance')->set('cache', 1)->save();
 
     // Create poll.
     $title = $this->randomName();
diff --git a/core/modules/simpletest/tests/bootstrap.test b/core/modules/simpletest/tests/bootstrap.test
index fee8fcc..9d74434 100644
--- a/core/modules/simpletest/tests/bootstrap.test
+++ b/core/modules/simpletest/tests/bootstrap.test
@@ -116,9 +116,7 @@ class BootstrapPageCacheTestCase extends DrupalWebTestCase {
    * Test support for requests containing If-Modified-Since and If-None-Match headers.
    */
   function testConditionalRequests() {
-    $config = config('system.performance');
-    $config->set('cache', 1);
-    $config->save();
+    config('system.performance')->set('cache', 1)->save();
 
     // Fill the cache.
     $this->drupalGet('');
@@ -156,9 +154,7 @@ class BootstrapPageCacheTestCase extends DrupalWebTestCase {
    * Test cache headers.
    */
   function testPageCache() {
-    $config = config('system.performance');
-    $config->set('cache', 1);
-    $config->save();
+    config('system.performance')->set('cache', 1)->save();
 
     // Fill the cache.
     $this->drupalGet('system-test/set-header', array('query' => array('name' => 'Foo', 'value' => 'bar')));
@@ -202,9 +198,7 @@ class BootstrapPageCacheTestCase extends DrupalWebTestCase {
    * mod_deflate Apache module.
    */
   function testPageCompression() {
-    $config = config('system.performance');
-    $config->set('cache', 1);
-    $config->save();
+    config('system.performance')->set('cache', 1)->save();
 
     // Fill the cache and verify that output is compressed.
     $this->drupalGet('', array(), array('Accept-Encoding: gzip,deflate'));
@@ -298,17 +292,14 @@ class HookBootExitTestCase extends DrupalWebTestCase {
   function testHookBootExit() {
     // Test with cache disabled. Boot and exit should always fire.
     $config = config('system.performance');
-    $config->set('cache', 0);
-    $config->save();
-
+    $config->set('cache', 0)->save();
     $this->drupalGet('');
     $calls = 1;
     $this->assertEqual(db_query('SELECT COUNT(*) FROM {watchdog} WHERE type = :type AND message = :message', array(':type' => 'system_test', ':message' => 'hook_boot'))->fetchField(), $calls, t('hook_boot called with disabled cache.'));
     $this->assertEqual(db_query('SELECT COUNT(*) FROM {watchdog} WHERE type = :type AND message = :message', array(':type' => 'system_test', ':message' => 'hook_exit'))->fetchField(), $calls, t('hook_exit called with disabled cache.'));
 
     // Test with normal cache. Boot and exit should be called.
-    $config->set('cache', 1);
-    $config->save();
+    $config->set('cache', 1)->save();
     $this->drupalGet('');
     $calls++;
     $this->assertEqual(db_query('SELECT COUNT(*) FROM {watchdog} WHERE type = :type AND message = :message', array(':type' => 'system_test', ':message' => 'hook_boot'))->fetchField(), $calls, t('hook_boot called with normal cache.'));
diff --git a/core/modules/simpletest/tests/cache.test b/core/modules/simpletest/tests/cache.test
index 81f2377..b9fdf8d 100644
--- a/core/modules/simpletest/tests/cache.test
+++ b/core/modules/simpletest/tests/cache.test
@@ -95,9 +95,7 @@ class CacheTestCase extends DrupalWebTestCase {
    *   The time in seconds the cache should minimal live.
    */
   protected function setupLifetime($time) {
-    $config = config('system.performance');
-    $config->set('cache_lifetime', $time);
-    $config->save();
+    config('system.performance')->set('cache_lifetime', $time)->save();
     variable_set('cache_flush', 0);
   }
 }
diff --git a/core/modules/simpletest/tests/common.test b/core/modules/simpletest/tests/common.test
index a681cf1..d6ec223 100644
--- a/core/modules/simpletest/tests/common.test
+++ b/core/modules/simpletest/tests/common.test
@@ -1173,8 +1173,7 @@ class CommonJavaScriptTestCase extends DrupalWebTestCase {
     // Disable preprocessing
     $config = config('system.performance');
     $this->preprocess_js = $config->get('preprocess_js');
-    $config->set('preprocess_js', 0);
-    $config->save();
+    $config->set('preprocess_js', 0)->save();
 
     // Reset drupal_add_js() and drupal_add_library() statics before each test.
     drupal_static_reset('drupal_add_js');
@@ -1184,8 +1183,7 @@ class CommonJavaScriptTestCase extends DrupalWebTestCase {
   function tearDown() {
     // Restore configured value for JavaScript preprocessing.
     $config = config('system.performance');
-    $config->set('preprocess_js', $this->preprocess_js);
-    $config->save();
+    $config->set('preprocess_js', $this->preprocess_js)->save();
     parent::tearDown();
   }
 
@@ -1383,9 +1381,7 @@ class CommonJavaScriptTestCase extends DrupalWebTestCase {
     // Now ensure that with aggregation on, one file is made for the
     // 'every_page' files, and one file is made for the others.
     drupal_static_reset('drupal_add_js');
-    $config = config('system.performance');
-    $config->set('preprocess_js', 1);
-    $config->save();
+    config('system.performance')->set('preprocess_js', 1)->save();
     drupal_add_js('core/misc/ajax.js');
     drupal_add_js('core/misc/authorize.js', array('every_page' => TRUE));
     drupal_add_js('core/misc/autocomplete.js');
diff --git a/core/modules/simpletest/tests/session.test b/core/modules/simpletest/tests/session.test
index 6303ca5..e5cfbff 100644
--- a/core/modules/simpletest/tests/session.test
+++ b/core/modules/simpletest/tests/session.test
@@ -139,9 +139,7 @@ class SessionTestCase extends DrupalWebTestCase {
     $this->assertSessionEmpty(TRUE);
 
     // The same behavior is expected when caching is enabled.
-    $config = config('system.performance');
-    $config->set('cache', 1);
-    $config->save();
+    config('system.performance')->set('cache', 1)->save();
     $this->drupalGet('');
     $this->assertSessionCookie(FALSE);
     $this->assertSessionEmpty(TRUE);
diff --git a/core/modules/simpletest/tests/theme.test b/core/modules/simpletest/tests/theme.test
index 0ed109d..d830106 100644
--- a/core/modules/simpletest/tests/theme.test
+++ b/core/modules/simpletest/tests/theme.test
@@ -93,8 +93,7 @@ class ThemeUnitTest extends DrupalWebTestCase {
     // so it doesn't matter what page we get, as long as it is themed with the
     // test theme. First we test with CSS aggregation disabled.
     $config = config('system.performance');
-    $config->set('preprocess_css', 0);
-    $config->save();
+    $config->set('preprocess_css', 0)->save();
     $this->drupalGet('theme-test/suggestion');
     $this->assertNoText('system.base.css', t('The theme\'s .info file is able to override a module CSS file from being added to the page.'));
 
@@ -102,11 +101,9 @@ class ThemeUnitTest extends DrupalWebTestCase {
     // triggered during drupal_build_css_cache() when a source file doesn't
     // exist. Then allow remaining tests to continue with aggregation disabled
     // by default.
-    $config->set('preprocess_css', 1);
-    $config->save();
+    $config->set('preprocess_css', 1)->save();
     $this->drupalGet('theme-test/suggestion');
-    $config->set('preprocess_css', 0);
-    $config->save();
+    $config->set('preprocess_css', 0)->save();
   }
 
   /**
diff --git a/core/modules/statistics/statistics.test b/core/modules/statistics/statistics.test
index 7fac22c..ae4b6ed 100644
--- a/core/modules/statistics/statistics.test
+++ b/core/modules/statistics/statistics.test
@@ -69,9 +69,7 @@ class StatisticsLoggingTestCase extends DrupalWebTestCase {
     $this->node = $this->drupalCreateNode(array('title' => $this->randomName(255), 'uid' => $this->auth_user->uid));
 
     // Enable page caching.
-    $config = config('system.performance');
-    $config->set('cache', 1);
-    $config->save();
+    config('system.performance')->set('cache', TRUE)->save();
 
     // Enable access logging.
     variable_set('statistics_enable_access_log', 1);
diff --git a/core/modules/system/system.admin.inc b/core/modules/system/system.admin.inc
index abe1577..1cbbe10 100644
--- a/core/modules/system/system.admin.inc
+++ b/core/modules/system/system.admin.inc
@@ -1652,14 +1652,14 @@ function system_performance_settings($form, &$form_state) {
     '#title' => t('Minimum cache lifetime'),
     '#default_value' => $config->get('cache_lifetime'),
     '#options' => $period,
-    '#description' => t('Cached pages will not be re-created until at least this much time has elapsed.'),
+    '#description' => t('Cached pages will not be re-created until at least this much time has elapsed.')
   );
   $form['caching']['page_cache_maximum_age'] = array(
     '#type' => 'select',
     '#title' => t('Expiration of cached pages'),
     '#default_value' => $config->get('page_cache_maximum_age'),
     '#options' => $period,
-    '#description' => t('The maximum time an external cache can use an old version of a page.'),
+    '#description' => t('The maximum time an external cache can use an old version of a page.')
   );
 
   $directory = 'public://';
@@ -1703,12 +1703,12 @@ function system_performance_settings($form, &$form_state) {
     '#value' => t('Save configuration'),
   );
 
+  $form['#submit'][] = 'system_performance_settings_submit';
   $form['#submit'][] = 'drupal_clear_css_cache';
   $form['#submit'][] = 'drupal_clear_js_cache';
   // This form allows page compression settings to be changed, which can
   // invalidate the page cache, so it needs to be cleared on form submit.
   $form['#submit'][] = 'system_clear_page_cache_submit';
-  $form['#submit'][] = 'system_performance_settings_submit';
 
   return $form;
 }
diff --git a/core/modules/system/system.install b/core/modules/system/system.install
index 8c34a1d..e98a4fd 100644
--- a/core/modules/system/system.install
+++ b/core/modules/system/system.install
@@ -716,7 +716,6 @@ function system_schema() {
     'primary key' => array('name'),
   );
 
-
   $schema['date_format_type'] = array(
     'description' => 'Stores configured date format types.',
     'fields' => array(