[Android WebView] Implement the capture picture API.

android_webview/browser/renderer_host/aw_render_view_host_ext.h

Index: android_webview/browser/renderer_host/aw_render_view_host_ext.h
diff --git a/android_webview/browser/renderer_host/aw_render_view_host_ext.h b/android_webview/browser/renderer_host/aw_render_view_host_ext.h
index 9848ba50566044339c6294da23d533147a4c885b..80a575e9592d3ca0d58d3fea1c5d4ae84ac3aece 100644
--- a/android_webview/browser/renderer_host/aw_render_view_host_ext.h
+++ b/android_webview/browser/renderer_host/aw_render_view_host_ext.h
@@ -57,6 +57,14 @@ class AwRenderViewHostExt : public content::WebContentsObserver,
   // the corresponding public WebView API is as well.
   const AwHitTestData& GetLastHitTestData() const;
 
+  // Enables updating picture piles on every new frame.
+  // OnPictureUpdated is called when a new picture is available,
+  // stored by renderer id in RendererPictureMap.
+  void EnableCapturePictureCallback(bool enabled);
+
+  // Captures the latest available picture pile synchronously.
+  void CapturePictureSync();
+
  private:
   // content::WebContentsObserver implementation.
   virtual void RenderViewGone(base::TerminationStatus status) OVERRIDE;
@@ -69,6 +77,8 @@ class AwRenderViewHostExt : public content::WebContentsObserver,
   void OnUpdateHitTestData(const AwHitTestData& hit_test_data);
   void OnPictureUpdated();
 
+  bool IsRenderViewReady() const;
+
   std::map<int, DocumentHasImagesResult> pending_document_has_images_requests_;
 
   // Master copy of hit test data on the browser side. This is updated