Expose locks for CopyFromCompositingSurface/CopyFromBackingStore API

content/public/browser/render_widget_host.h

Index: content/public/browser/render_widget_host.h
diff --git a/content/public/browser/render_widget_host.h b/content/public/browser/render_widget_host.h
index 2eb913b2ab54edd40aac2a52045b46088b37cba3..3140af52362e7f86a248022f5a9e3e680c641e91 100644
--- a/content/public/browser/render_widget_host.h
+++ b/content/public/browser/render_widget_host.h
@@ -200,6 +200,9 @@ class CONTENT_EXPORT RenderWidgetHost : public IPC::Sender {
       const gfx::Rect& src_rect,
       const gfx::Size& accelerated_dst_size,
       const base::Callback<void(bool, const SkBitmap&)>& callback) = 0;
+  // Ensures that the view does not drop the backing store even when hidden.
+  virtual void LockForCopyFromBackingStore() = 0;
+  virtual void UnlockForCopyFromBackingStore() = 0;
 #if defined(TOOLKIT_GTK)
   // Paint the backing store into the target's |dest_rect|.
   virtual bool CopyFromBackingStoreToGtkWindow(const gfx::Rect& dest_rect,