gesture recognizer: Recognizer rotation gestures.

ui/base/gestures/gesture_types.h

Index: ui/base/gestures/gesture_types.h
diff --git a/ui/base/gestures/gesture_types.h b/ui/base/gestures/gesture_types.h
index d44de87f119b9107b295a5d7e3938241a5d90015..2e8ef2c4f49d36f3c212edea0413f589ad193904 100644
--- a/ui/base/gestures/gesture_types.h
+++ b/ui/base/gestures/gesture_types.h
@@ -60,7 +60,12 @@ struct UI_EXPORT GestureEventDetails {
 
   float scale() const {
     CHECK_EQ(ui::ET_GESTURE_PINCH_UPDATE, type_);
-    return data.scale;
+    return data.pinch.scale;
+  }
+
+  float rotation() const {
+    CHECK_EQ(ui::ET_GESTURE_PINCH_UPDATE, type_);
+    return data.pinch.rotation;
   }
 
   bool swipe_left() const {
@@ -98,7 +103,10 @@ struct UI_EXPORT GestureEventDetails {
       float velocity_y;
     } scroll_update;
 
-    float scale;  // PINCH scale.
+    struct {  // PINCH scale, rotation.
+      float scale;
+      float rotation;
+    } pinch;
 
     struct {  // FLING velocity.
       float x;