Account for failure of coordinate space transformations in browser

content/browser/frame_host/cross_process_frame_connector.h

 // Copyright 2014 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #ifndef CONTENT_BROWSER_FRAME_HOST_CROSS_PROCESS_FRAME_CONNECTOR_H_
 #define CONTENT_BROWSER_FRAME_HOST_CROSS_PROCESS_FRAME_CONNECTOR_H_
 
 #include <stdint.h>
 
 #include "cc/output/compositor_frame.h"
@@ skipping 80 matching lines @@
                                     float scale_factor,
                                     const cc::SurfaceSequence& sequence);
 
   gfx::Rect ChildFrameRect();
   void UpdateCursor(const WebCursor& cursor);
   gfx::Point TransformPointToRootCoordSpace(const gfx::Point& point,
                                             const cc::SurfaceId& surface_id);
   // TransformPointToLocalCoordSpace() can only transform points between
   // surfaces where one is embedded (not necessarily directly) within the
   // other. For points that can be in sibling surfaces, they must first be
   // converted to the root surface's coordinate space.

[ncarter (slow), 2016/10/13 20:34:42]

Document the return value (and maybe give an example of why failure might
occur?).

[kenrb, 2016/10/14 13:02:43]

Done.

-  gfx::Point TransformPointToLocalCoordSpace(
-      const gfx::Point& point,
-      const cc::SurfaceId& original_surface,
-      const cc::SurfaceId& local_surface_id);
-  gfx::Point TransformPointToCoordSpaceForView(
-      const gfx::Point& point,
-      RenderWidgetHostViewBase* target_view,
-      const cc::SurfaceId& local_surface_id);
+  bool TransformPointToLocalCoordSpace(const gfx::Point& point,
+                                       const cc::SurfaceId& original_surface,
+                                       const cc::SurfaceId& local_surface_id,
+                                       gfx::Point* transformed_point);
+  bool TransformPointToCoordSpaceForView(const gfx::Point& point,
+                                         RenderWidgetHostViewBase* target_view,
+                                         const cc::SurfaceId& local_surface_id,
+                                         gfx::Point* transformed_point);
 
   // Pass acked touch events to the root view for gesture processing.
   void ForwardProcessAckedTouchEvent(const TouchEventWithLatencyInfo& touch,
                                      InputEventAckState ack_result);
   // Gesture events with unused scroll deltas must be bubbled to ancestors
   // who may consume the delta.
   void BubbleScrollEvent(const blink::WebGestureEvent& event);
 
   // Determines whether the root RenderWidgetHostView (and thus the current
   // page) has focus.
@@ skipping 38 matching lines @@
 
   gfx::Rect child_frame_rect_;
 
   bool is_scroll_bubbling_;
 };
 
 }  // namespace content
 
 #endif  // CONTENT_BROWSER_FRAME_HOST_CROSS_PROCESS_FRAME_CONNECTOR_H_