diff --git a/core/lib/Drupal/Core/EventSubscriber/HtmlViewSubscriber.php b/core/lib/Drupal/Core/EventSubscriber/HtmlViewSubscriber.php
index ed2e87b..c777a33 100644
--- a/core/lib/Drupal/Core/EventSubscriber/HtmlViewSubscriber.php
+++ b/core/lib/Drupal/Core/EventSubscriber/HtmlViewSubscriber.php
@@ -60,11 +60,14 @@ public function onPartialHtmlResponse(GetResponseForControllerResultEvent $event
 
     // @todo this is really lazy, but the easiest way to get $page_{top,bottom}. this can be removed once the responsibility is shifted into displays/controllers
     $page = element_info('page');
-    foreach ($this->moduleHandler->getImplementations('page_build') as $module) {
-      $function = $module . '_page_build';
-      $function($page);
+
+    if ($event->getRequestType() === HttpKernelInterface::MASTER_REQUEST) {
+      foreach ($this->moduleHandler->getImplementations('page_build') as $module) {
+        $function = $module . '_page_build';
+        $function($page);
+      }
+      $this->moduleHandler->alter('page', $page);
     }
-    $this->moduleHandler->alter('page', $page);
 
     // @todo these are horrible passthrough hacks; remove them incrementally as we implement the respective pieces elsewhere.
     $vars = array(
diff --git a/core/lib/Drupal/Core/PartialResponse.php b/core/lib/Drupal/Core/PartialResponse.php
index 43694b0..8976e64 100644
--- a/core/lib/Drupal/Core/PartialResponse.php
+++ b/core/lib/Drupal/Core/PartialResponse.php
@@ -61,22 +61,6 @@ public function getContent() {
   }
 
   /**
-   * Adds another meta tag, to be output in HTML head.
-   *
-   * @param $tag
-   */
-  public function addMetaTag($tag) {
-    // @todo implement this
-  }
-
-  /**
-   * Gets all meta tags for output.
-   */
-  public function getMetaTags() {
-    // @todo implement this
-  }
-
-  /**
    * Sets the title of this PartialResponse.
    *
    * Handling of this title varies depending on what is consuming this
@@ -105,24 +89,4 @@ public function hasTitle() {
   public function getTitle() {
     return $this->title;
   }
-
-  /**
-   * Sets the AssetBag for this PartialResponse.
-   *
-   * The AssetBag has all of its own logic for sorting out assets and deciding
-   * where they should go; the PartialResponse is only response for carrying it
-   * around.
-   *
-   * @todo https://drupal.org/node/1762204
-   */
-  public function setAssetBag() {
-
-  }
-
-  /**
-   * Returns the AssetBag contained by this PartialResponse.
-   */
-  public function getAssetBag() {
-
-  }
 }