Synthetic pinch gesture take scale factor as parameter.

content/browser/renderer_host/input/synthetic_gesture_target.h

 // Copyright 2013 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #ifndef CONTENT_BROWSER_RENDERER_HOST_INPUT_SYNTHETIC_GESTURE_TARGET_H_
 #define CONTENT_BROWSER_RENDERER_HOST_INPUT_SYNTHETIC_GESTURE_TARGET_H_
 
 #include "base/time/time.h"
 #include "content/browser/renderer_host/input/synthetic_gesture.h"
 #include "content/common/content_export.h"
@@ skipping 24 matching lines @@
   // Returns the default gesture source type for the target.
   virtual SyntheticGestureParams::GestureSourceType
       GetDefaultSyntheticGestureSourceType() const = 0;
 
   // After how much time of inaction does the target assume that a pointer has
   // stopped moving.
   virtual base::TimeDelta PointerAssumedStoppedTime() const = 0;
 
   // 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
 
 #endif  // CONTENT_BROWSER_RENDERER_HOST_INPUT_SYNTHETIC_GESTURE_TARGET_H_