Rewire Android WebView's compositor changed signal.

android_webview/native/aw_contents.h

Index: android_webview/native/aw_contents.h
diff --git a/android_webview/native/aw_contents.h b/android_webview/native/aw_contents.h
index 5062eb88ea5f34f303be2608d210a26ae8def30f..12ff238e9936b929ba74e450407767f6caec0f93 100644
--- a/android_webview/native/aw_contents.h
+++ b/android_webview/native/aw_contents.h
@@ -27,6 +27,7 @@
 #include "base/android/scoped_java_ref.h"
 #include "base/callback_forward.h"
 #include "base/macros.h"
+#include "content/public/browser/web_contents_observer.h"
 
 class SkBitmap;
 class TabContents;
@@ -64,7 +65,8 @@ class AwContents : public FindHelper::Listener,
                    public AwRenderViewHostExtClient,
                    public BrowserViewRendererClient,
                    public PermissionRequestHandlerClient,
-                   public AwBrowserPermissionRequestDelegate {
+                   public AwBrowserPermissionRequestDelegate,
+                   public content::WebContentsObserver {
  public:
   // Returns the AwContents instance associated with |web_contents|, or NULL.
   static AwContents* FromWebContents(content::WebContents* web_contents);
@@ -333,6 +335,10 @@ class AwContents : public FindHelper::Listener,
       JNIEnv* env,
       const base::android::JavaParamRef<jobject>& obj);
 
+  // content::WebContentsObserver overrides
+  void RenderViewHostChanged(content::RenderViewHost* old_host,
+                             content::RenderViewHost* new_host) override;
+
  private:
   void InitAutofillIfNecessary(bool enabled);
 
@@ -347,9 +353,9 @@ class AwContents : public FindHelper::Listener,
   JavaObjectWeakGlobalRef java_ref_;
   AwGLFunctor* functor_;
   BrowserViewRenderer browser_view_renderer_;  // Must outlive |web_contents_|.
+  std::unique_ptr<content::WebContents> web_contents_;
   std::unique_ptr<AwWebContentsDelegate> web_contents_delegate_;
   std::unique_ptr<AwContentsClientBridge> contents_client_bridge_;
-  std::unique_ptr<content::WebContents> web_contents_;
   std::unique_ptr<AwRenderViewHostExt> render_view_host_ext_;
   std::unique_ptr<FindHelper> find_helper_;
   std::unique_ptr<IconHelper> icon_helper_;