Fix assert in GetOverlayRect when transforming video with Ozone overlay

ui/ozone/public/overlay_candidates_ozone.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 UI_OZONE_PUBLIC_OVERLAY_CANDIDATES_OZONE_H_
 #define UI_OZONE_PUBLIC_OVERLAY_CANDIDATES_OZONE_H_
 
 #include <vector>
 
 #include "base/basictypes.h"
 #include "ui/gfx/geometry/rect_f.h"
 #include "ui/ozone/ozone_base_export.h"
 #include "ui/ozone/public/surface_factory_ozone.h"
 
 namespace ui {
 
 // This class can be used to answer questions about possible overlay
 // configurations for a particular output device. We get an instance of this
 // class from SurfaceFactoryOzone given an AcceleratedWidget.
 class OZONE_BASE_EXPORT OverlayCandidatesOzone {
  public:
   struct OverlaySurfaceCandidate {
     OverlaySurfaceCandidate();
     ~OverlaySurfaceCandidate();
 
     // Transformation to apply to layer during composition.
     gfx::OverlayTransform transform;
     // Format of the buffer to composite.
     SurfaceFactoryOzone::BufferFormat format;
-    // Rect on the display to position the overlay to.
-    gfx::Rect display_rect;
+    // Rect on the display to position the overlay to. Input rectangle may
+    // not have integer coordinates, but when accepting for overlay, must
+    // be modified by CheckOverlaySupport to output integer values.
+    gfx::RectF display_rect;
     // Crop within the buffer to be placed inside |display_rect|.
     gfx::RectF crop_rect;
     // 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<OverlaySurfaceCandidate> OverlaySurfaceCandidateList;
 
   // A list of possible overlay candidates is presented to this function.
   // The expected result is that those candidates that can be in a separate
   // plane are marked with |overlay_handled| set to true, otherwise they are
-  // to be tranditionally composited.
+  // to be traditionally composited. When setting |overlay_handled| to true,
+  // the implementation must also snap |display_rect| to integer coordinates
+  // if necessary.
   virtual void CheckOverlaySupport(OverlaySurfaceCandidateList* surfaces);
 
   virtual ~OverlayCandidatesOzone();
 };
 
 }  // namespace ui
 
 #endif  // UI_OZONE_PUBLIC_OVERLAY_CANDIDATES_OZONE_H_