Invert DSF to map from delegated frame to layer space

cc/output/delegated_frame_data.h

 // Copyright 2012 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_DELEGATED_FRAME_DATA_H_
 #define CC_OUTPUT_DELEGATED_FRAME_DATA_H_
 
 #include "cc/base/cc_export.h"
 #include "cc/base/scoped_ptr_vector.h"
 #include "cc/quads/render_pass.h"
 #include "cc/resources/transferable_resource.h"
 #include "ui/gfx/size.h"
 
 namespace cc {
 
 class CC_EXPORT DelegatedFrameData {
  public:
   DelegatedFrameData();
   ~DelegatedFrameData();
 
+  // The device scale factor used when generating this frame.
+  float device_scale_factor;

[danakj, 2014/06/10 15:44:57]

This is already available in CompositorFrameMetadata
https://code.google.com/p/chromium/codesearch#chromium/src/cc/output/composit...

+
   TransferableResourceArray resource_list;
   ScopedPtrVector<RenderPass> render_pass_list;
 
  private:
   DISALLOW_COPY_AND_ASSIGN(DelegatedFrameData);
 };
 
 }  // namespace cc
 
 #endif  // CC_OUTPUT_DELEGATED_FRAME_DATA_H_