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..14724bf67f906436fa1331445180a9994dcdb7a5 100644
--- a/content/browser/renderer_host/input/synthetic_gesture_target.h
+++ b/content/browser/renderer_host/input/synthetic_gesture_target.h
@@ -42,7 +42,11 @@ 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;
+  virtual float GetTouchSlopInDips() const = 0;
+
+  // Returns the minimum number of DIPs two touch pointers have to be apart
+  // to perform a pinch-zoom.
+  virtual float GetMinScalingSpanInDips() const = 0;
 };
 
 }  // namespace content