Expose locks for CopyFromCompositingSurface/CopyFromBackingStore API

content/port/browser/render_widget_host_view_port.h

Index: content/port/browser/render_widget_host_view_port.h
diff --git a/content/port/browser/render_widget_host_view_port.h b/content/port/browser/render_widget_host_view_port.h
index ae00425b9fcf91ce8fd7127669dd29959d213539..0a2f57d911f4d4971016cc44acd051d3298a2ebf 100644
--- a/content/port/browser/render_widget_host_view_port.h
+++ b/content/port/browser/render_widget_host_view_port.h
@@ -184,6 +184,11 @@ class CONTENT_EXPORT RenderWidgetHostViewPort : public RenderWidgetHostView,
       const base::Callback<void(bool, const SkBitmap&)>& callback,
       const SkBitmap::Config config) = 0;
 
+  // For async implementation of copy, we provide a lock to ensure that the
+  // content is not evicted while copying.

[no sievers, 2014/02/21 02:34:10]

I'd say that it instructs the view to not drop the surface even when the view is
hidden.

I'd also put a comment in the public interface.

[powei, 2014/02/21 18:41:15]

Done.

+  virtual void LockSurfaceForCopy() = 0;
+  virtual void UnlockSurfaceForCopy() = 0;
+
   // Copies a given subset of the compositing surface's content into a YV12
   // VideoFrame, and invokes a callback with a success/fail parameter. |target|
   // must contain an allocated, YV12 video frame of the intended size. If the