Clean up GestureEventDetails constructors

ui/events/gesture_event_details.h

 // Copyright 2014 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 UI_EVENTS_GESTURE_DETECTION_GESTURE_EVENT_DETAILS_H_
 #define UI_EVENTS_GESTURE_DETECTION_GESTURE_EVENT_DETAILS_H_
 
 #include "base/logging.h"
 #include "ui/events/event_constants.h"
 #include "ui/events/events_base_export.h"
 #include "ui/gfx/rect.h"
 #include "ui/gfx/rect_conversions.h"
 
 namespace ui {
 
 struct EVENTS_BASE_EXPORT GestureEventDetails {
  public:
   GestureEventDetails();
+  GestureEventDetails(EventType type);
   GestureEventDetails(EventType type, float delta_x, float delta_y);
 
   EventType type() const { return type_; }
 
   int touch_points() const { return touch_points_; }
   void set_touch_points(int touch_points) {
     DCHECK_GT(touch_points, 0);
     touch_points_ = touch_points;
   }
 
@@ skipping 87 matching lines @@
   }
 
   void set_tap_count(int tap_count) {
     DCHECK_GE(tap_count, 0);
     DCHECK(type_ == ET_GESTURE_TAP ||
            type_ == ET_GESTURE_TAP_UNCONFIRMED ||
            type_ == ET_GESTURE_DOUBLE_TAP);
     data.tap_count = tap_count;
   }
 
+  void set_scale(float scale) {
+    DCHECK_GE(scale, 0.0f);
+    DCHECK_EQ(type_, ET_GESTURE_PINCH_UPDATE);
+    data.scale = scale;
+  }
+
  private:
   EventType type_;
   union Details {
     Details();
     struct {  // SCROLL start details.
       // Distance that caused the scroll to start.  Generally redundant with
       // the x/y values from the first scroll_update.
       float x_hint;
       float y_hint;
     } scroll_begin;
@@ skipping 35 matching lines @@
   // enclosing rectangles of the touch-points in the gesture.
   gfx::RectF bounding_box_;
 
   // The touch id of the oldest touch contributing to the gesture.
   int oldest_touch_id_;
 };
 
 }  // namespace ui
 
 #endif  // UI_EVENTS_GESTURE_DETECTION_GESTURE_EVENT_DETAILS_H_