Add touchpad pinch zoom support to Blink

Source/core/frame/PinchViewport.h

Index: Source/core/frame/PinchViewport.h
diff --git a/Source/core/frame/PinchViewport.h b/Source/core/frame/PinchViewport.h
index 8964414e718352c2d1759fd1faa3431af5680b42..c3d025be06a301f23abcf38c1f5120d996a96add 100644
--- a/Source/core/frame/PinchViewport.h
+++ b/Source/core/frame/PinchViewport.h
@@ -106,6 +106,9 @@ public:
     void setScale(float);
     float scale() const { return m_scale; }
 
+    // Update scale factor, magnifying or minifying around specified anchor.
+    void setScaleAroundAnchor(float scale, const FloatPoint& anchor);

[bokan, 2015/02/03 03:05:16]

Could you also add a comment or name anchor so it's clear what coordinates it's
in? I assume window?

[ccameron, 2015/02/03 17:03:28]

Done.

+
     void registerLayersWithTreeView(blink::WebLayerTreeView*) const;
     void clearLayersForTreeView(blink::WebLayerTreeView*) const;