Implement desktop compatibility viewport

cc/layer_tree_host_common.h

 // Copyright 2011 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_LAYER_TREE_HOST_COMMON_H_
 #define CC_LAYER_TREE_HOST_COMMON_H_
 
 #include "base/memory/ref_counted.h"
 #include "cc/cc_export.h"
 #include "cc/scoped_ptr_vector.h"
@@ skipping 41 matching lines @@
         gfx::Vector2d scrollDelta;
     };
 };
 
 struct CC_EXPORT ScrollAndScaleSet {
     ScrollAndScaleSet();
     ~ScrollAndScaleSet();
 
     std::vector<LayerTreeHostCommon::ScrollUpdateInfo> scrolls;
     float pageScaleDelta;
+    gfx::Vector2d desktopCompatibilityViewportOffsetFromScrollPositionDelta;
 };
 
 template<typename LayerType>
 bool LayerTreeHostCommon::renderSurfaceContributesToTarget(LayerType* layer, int targetSurfaceLayerID)
 {
     // A layer will either contribute its own content, or its render surface's content, to
     // the target surface. The layer contributes its surface's content when both the
     // following are true:
     //  (1) The layer actually has a renderSurface, and
     //  (2) The layer's renderSurface is not the same as the targetSurface.
@@ skipping 18 matching lines @@
     for (size_t i = 0; i < rootLayer->children().size(); ++i) {
         if (LayerType* found = findLayerInSubtree(getChildAsRawPtr(rootLayer->children(), i), layerId))
             return found;
     }
     return 0;
 }
 
 }  // namespace cc
 
 #endif  // CC_LAYER_TREE_HOST_COMMON_H_