Android:Allow a read-back request to wait for a first frame

content/browser/renderer_host/render_widget_host_view_android.h

Index: content/browser/renderer_host/render_widget_host_view_android.h
diff --git a/content/browser/renderer_host/render_widget_host_view_android.h b/content/browser/renderer_host/render_widget_host_view_android.h
index 0468278b063321d7d3d77d006eb4e85bae5f1d5d..52831f0c698370398ee6b9054f2a943b65664afa 100644
--- a/content/browser/renderer_host/render_widget_host_view_android.h
+++ b/content/browser/renderer_host/render_widget_host_view_android.h
@@ -58,6 +58,33 @@ class RenderWidgetHostImpl;
 struct DidOverscrollParams;
 struct NativeWebKeyboardEvent;
 
+class ReadbackRequest {
+ public:
+  explicit ReadbackRequest(
+      float scale,
+      SkColorType color_type,
+      gfx::Rect src_subrect,
+      const base::Callback<void(bool, const SkBitmap&)>& result_callback)
+      : scale_(scale),
+        color_type_(color_type),
+        src_subrect_(src_subrect),
+        result_callback_(result_callback) {}
+  ~ReadbackRequest() {};
+  float GetScale() { return scale_; }
+  SkColorType GetColorFormat() { return color_type_; }
+  gfx::Rect GetCaptureRect() { return src_subrect_; }

[no sievers, 2014/07/28 17:07:06]

nit: return a reference for the rect

+  const base::Callback<void(bool, const SkBitmap&)>& GetResultCallback() {
+    return result_callback_;
+  }
+
+ private:
+  ReadbackRequest() {};
+  float scale_;
+  SkColorType color_type_;
+  gfx::Rect src_subrect_;
+  base::Callback<void(bool, const SkBitmap&)> result_callback_;
+};
+
 // -----------------------------------------------------------------------------
 // See comments in render_widget_host_view.h about this class and its members.
 // -----------------------------------------------------------------------------
@@ -315,6 +342,12 @@ class CONTENT_EXPORT RenderWidgetHostViewAndroid
 
   float GetDpiScale() const;
 
+  // Add the ReadbackRequest to the queue and wait for frame arraival.

[no sievers, 2014/07/28 17:07:06]

not: typo in 'arraival'

+  void WaitForValidFrameArrival(const ReadbackRequest& readback_request);

[no sievers, 2014/07/28 17:07:06]

nit: How about a more specific name? Something like 'DeferReadback' or so.

+
+  // Handles all unprocessed and pending readback requests.
+  void ProcessPendingReadbackRequests();
+
   // The model object.
   RenderWidgetHostImpl* host_;
 
@@ -395,6 +428,9 @@ class CONTENT_EXPORT RenderWidgetHostViewAndroid
 
   TextSurroundingSelectionCallback text_surrounding_selection_callback_;
 
+  // List of readbackrequests waiting for arrival of a valid frame.
+  std::queue<ReadbackRequest> readbacks_waiting_for_frame_;
+
   DISALLOW_COPY_AND_ASSIGN(RenderWidgetHostViewAndroid);
 };