Support bottom-right anchored fixed-position elements during a pinch gesture

cc/layer_impl.h

Index: cc/layer_impl.h
diff --git a/cc/layer_impl.h b/cc/layer_impl.h
index a325aa0bbfd34df9a3f4c7685dd3a0a2a313df71..da2a60404ff3bf9d2768e9a1915483fc89fcf85c 100644
--- a/cc/layer_impl.h
+++ b/cc/layer_impl.h
@@ -152,9 +152,18 @@ public:
     void setIsContainerForFixedPositionLayers(bool isContainerForFixedPositionLayers) { m_isContainerForFixedPositionLayers = isContainerForFixedPositionLayers; }
     bool isContainerForFixedPositionLayers() const { return m_isContainerForFixedPositionLayers; }
 
+    void setFixedContainerSizeDelta(const gfx::Vector2dF& fixedContainerSizeDelta) { m_fixedContainerSizeDelta = fixedContainerSizeDelta; }
+    const gfx::Vector2dF& fixedContainerSizeDelta() const { return m_fixedContainerSizeDelta; }
+
     void setFixedToContainerLayer(bool fixedToContainerLayer = true) { m_fixedToContainerLayer = fixedToContainerLayer;}
     bool fixedToContainerLayer() const { return m_fixedToContainerLayer; }
 
+    void setFixedToRightEdge(bool fixedToRightEdge) { m_fixedToRightEdge = fixedToRightEdge; }
+    bool fixedToRightEdge() const { return m_fixedToRightEdge; }
+
+    void setFixedToBottomEdge(bool fixedToBottomEdge) { m_fixedToBottomEdge = fixedToBottomEdge; }
+    bool fixedToBottomEdge() const { return m_fixedToBottomEdge; }
+
     void setPreserves3D(bool);
     bool preserves3D() const { return m_preserves3D; }
 
@@ -389,8 +398,16 @@ private:
 
     // Set for the layer that other layers are fixed to.
     bool m_isContainerForFixedPositionLayers;
+    // This property is effective when m_isContainerForFixedPositionLayers == true,
+    // Currently the only fixed container that resizes is the main frame

[shawnsingh, 2013/03/07 09:57:06]

I imagine that it will be easy to overlook updating this comment if we ever have
to change it.   Also, we should be able to make this patch work for any
container layer that resizes (even though that wouldn't happen yet).  So my vote
is to remove this second sentence in this comment.

+    // scroll layer during a pinch gesture.
+    gfx::Vector2dF m_fixedContainerSizeDelta;
     // This is true if the layer should be fixed to the closest ancestor container.
     bool m_fixedToContainerLayer;
+    // These two properties are effective when m_fixedToContainerLayer == true,
+    // and only make sense if its fixed container resizes itself.
+    bool m_fixedToRightEdge;
+    bool m_fixedToBottomEdge;
 
     gfx::Vector2dF m_scrollDelta;
     gfx::Vector2d m_sentScrollDelta;