Add support for touch based zoom gesture on Windows. This change also handles the WM_POINTERDOWN

content/renderer/render_view_impl.h

Index: content/renderer/render_view_impl.h
===================================================================
--- content/renderer/render_view_impl.h	(revision 107314)
+++ content/renderer/render_view_impl.h	(working copy)
@@ -862,6 +862,9 @@
   void OnSelectPopupMenuItem(int selected_index);
 #endif
   void OnZoom(PageZoom::Function function);
+  void OnZoomFactor(PageZoom::Function function, int zoom_center_x,
+                    int zoom_center_y);
+
   void OnEnableViewSourceMode();
 
   void OnJavaBridgeInit(const IPC::ChannelHandle& channel_handle);
@@ -870,6 +873,8 @@
   // and put it in the same position in the .cc file.
 
   // Misc private functions ----------------------------------------------------
+  void ZoomFactorHelper(PageZoom::Function function, int zoom_center_x,
+                        int zoom_center_y, float scaling_increment);
 
   void AltErrorPageFinished(WebKit::WebFrame* frame,
                             const WebKit::WebURLError& original_error,