Synthetic pinch gesture take scale factor as parameter.

content/browser/renderer_host/input/synthetic_gesture_target.h

Index: content/browser/renderer_host/input/synthetic_gesture_target.h
diff --git a/content/browser/renderer_host/input/synthetic_gesture_target.h b/content/browser/renderer_host/input/synthetic_gesture_target.h
index b7bb2bab5a81fa36a817b4c9733e6c4935c53fdd..57ed423d27c8bf94fe4ad519749a230d61a62d8e 100644
--- a/content/browser/renderer_host/input/synthetic_gesture_target.h
+++ b/content/browser/renderer_host/input/synthetic_gesture_target.h
@@ -43,6 +43,10 @@ class CONTENT_EXPORT SyntheticGestureTarget {
   // Returns the maximum number of DIPs a touch pointer can move without being
   // considered moving by the platform.
   virtual int GetTouchSlopInDips() const = 0;

[jdduke (slow), 2014/05/19 15:21:11]

We should be returning floats for anything in DIPs.  There are no guarantees
that the Android constants will be integral.

[Dominik Grewe, 2014/05/19 17:31:43]

Done.

+
+  // Returns the minimum number of DIPs two touch pointers have to be apart
+  // to perform a pinch-zoom.
+  virtual int GetMinScalingSpanInDips() const = 0;
 };
 
 }  // namespace content