[Ozone] Fix SingleOnTop issue by checking if the quad is clipped.

cc/output/overlay_candidate.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 CC_OUTPUT_OVERLAY_CANDIDATE_H_
 #define CC_OUTPUT_OVERLAY_CANDIDATE_H_
 
 #include <vector>
 
 #include "cc/base/cc_export.h"
@@ skipping 23 matching lines @@
   gfx::OverlayTransform transform;
   // Format of the buffer to composite.
   ResourceFormat format;
   // Size of the resource, in pixels.
   gfx::Size resource_size_in_pixels;
   // Rect on the display to position the overlay to. Implementer must convert
   // to integer coordinates if setting |overlay_handled| to true.
   gfx::RectF display_rect;
   // Crop within the buffer to be placed inside |display_rect|.
   gfx::RectF uv_rect;
+
+  // Original visible area of the quad

[danakj, 2015/08/28 22:48:10]

period at the end

can you explain what you mean by original vs actual? original before what?
actual is after what?

I think these names may be misleading. One is the visible rect in the quad. One
is the visible bounds of the layer the quad came from. They are not even in the
same coordinate space, one is in layer space, one is in quad geometry space.

[william.xie1, 2015/08/28 23:18:42]

Hi Dana,
 Thanks for your comments.
My previous meaning is, original means before composition, actual means after
composition. From my testing, original rect doesn not change, it only reply on
the page scaling factor. Actual rect will change to the actual visible rect if
the quad is clipped.

So it is workable by comparing these two rects to decide if quad is clipped.
Do you agree on this?
also, do you think we should find good names to describe these two rects?

+  gfx::Rect original_visible_rect;
+
+  // Actual visible area of the quad

[danakj, 2015/08/28 22:48:09]

ditto

+  gfx::Rect actual_visible_rect;
+
   // Texture resource to present in an overlay.
   unsigned resource_id;
   // Stacking order of the overlay plane relative to the main surface,
   // which is 0. Signed to allow for "underlays".
   int plane_z_order;
 
   // To be modified by the implementer if this candidate can go into
   // an overlay.
   bool overlay_handled;
 };
 
 typedef std::vector<OverlayCandidate> OverlayCandidateList;
 
 }  // namespace cc
 
 #endif  // CC_OUTPUT_OVERLAY_CANDIDATE_H_