Implement transform/clip support for Android WebView.

cc/trees/layer_tree_host_impl.h

Index: cc/trees/layer_tree_host_impl.h
diff --git a/cc/trees/layer_tree_host_impl.h b/cc/trees/layer_tree_host_impl.h
index f65922aa8769dc7e50f2ef96cdba562d85d7fc7f..e3671cf052a46dd58162b9c3d651e3d30ef66fca 100644
--- a/cc/trees/layer_tree_host_impl.h
+++ b/cc/trees/layer_tree_host_impl.h
@@ -176,8 +176,8 @@ class CC_EXPORT LayerTreeHostImpl
   gfx::SizeF VisibleViewportSize() const;
 
   // RendererClient implementation
+  virtual gfx::Rect DeviceViewport() const OVERRIDE;
  private:
-  virtual gfx::Size DeviceViewportSize() const OVERRIDE;
   virtual float DeviceScaleFactor() const OVERRIDE;
   virtual const LayerTreeSettings& Settings() const OVERRIDE;
  public:
@@ -207,6 +207,8 @@ class CC_EXPORT LayerTreeHostImpl
       OVERRIDE;
   virtual void OnSendFrameToParentCompositorAck(const CompositorFrameAck& ack)
       OVERRIDE;
+  virtual void SetExternalDrawConstraints(const gfx::Transform& transform,
+                                          gfx::Rect viewport) OVERRIDE;
 
   // Called from LayerTreeImpl.
   void OnCanDrawStateChangedForTree();
@@ -267,6 +269,8 @@ class CC_EXPORT LayerTreeHostImpl
   void SetDeviceScaleFactor(float device_scale_factor);
   float device_scale_factor() const { return device_scale_factor_; }
 
+  const gfx::Transform& DeviceTransform() const;
+
   scoped_ptr<ScrollAndScaleSet> ProcessScrollDeltas();
 
   bool needs_animate_layers() const {
@@ -457,9 +461,6 @@ class CC_EXPORT LayerTreeHostImpl
   LayerScrollOffsetDelegate* root_layer_scroll_offset_delegate_;
   LayerTreeSettings settings_;
   LayerTreeDebugState debug_state_;
-  gfx::Size device_viewport_size_;
-  float overdraw_bottom_height_;
-  float device_scale_factor_;
   bool visible_;
   ManagedMemoryPolicy managed_memory_policy_;
 
@@ -493,6 +494,26 @@ class CC_EXPORT LayerTreeHostImpl
   size_t last_sent_memory_visible_and_nearby_bytes_;
   size_t last_sent_memory_use_bytes_;
 
+  // Viewport size passed in from the main thread, in physical pixels.
+  gfx::Size device_viewport_size_;
+
+  // Conversion factor from CSS pixels to physical pixels when
+  // pageScaleFactor=1.
+  float device_scale_factor_;
+
+  // Vertical amount of the viewport size that's known to covered by a
+  // browser-side UI element, such as an on-screen-keyboard.  This affects
+  // scrollable size since we want to still be able to scroll to the bottom of
+  // the page when the keyboard is up.
+  float overdraw_bottom_height_;
+
+  // Optional top-level constraints that can be set by the OutputSurface.  The
+  // external_viewport_'s size takes precedence over device_viewport_size_ for
+  // DrawQuad generation and Renderer; however, device_viewport_size_ is still
+  // used for scrollable size.
+  gfx::Transform external_transform_;
+  gfx::Rect external_viewport_;
+
   gfx::Rect viewport_damage_rect_;
 
   base::TimeTicks current_frame_timeticks_;