Make touch-based synthetic gesture take touch slop into account.

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 5b31b0294fb06e99fc288c50060bcd43747d0511..ce1a95207b722c14ced1d185ac0141f8b2aee16e 100644
--- a/content/browser/renderer_host/input/synthetic_gesture_target.h
+++ b/content/browser/renderer_host/input/synthetic_gesture_target.h
@@ -44,6 +44,10 @@ class CONTENT_EXPORT SyntheticGestureTarget {
   // After how much time of inaction does the target assume that a pointer has
   // stopped moving.
   virtual base::TimeDelta PointerAssumedStoppedTime() const = 0;
+
+  // Returns the number of DIPs a touch pointer has to move before it is
+  // considered moving by the platform.
+  virtual int GetTouchSlopInDips() const = 0;
 };
 
 }  // namespace content