Do not convert mouse wheel gesture events in pepper.

content/renderer/render_widget_fullscreen_pepper.cc

Index: content/renderer/render_widget_fullscreen_pepper.cc
diff --git a/content/renderer/render_widget_fullscreen_pepper.cc b/content/renderer/render_widget_fullscreen_pepper.cc
index 6f3dc9529835b04da0cfb30004d4b5cdc34c697c..30a6372c08274af15a6765680bd67ab280e6c81d 100644
--- a/content/renderer/render_widget_fullscreen_pepper.cc
+++ b/content/renderer/render_widget_fullscreen_pepper.cc
@@ -65,37 +65,31 @@ class FullscreenMouseLockDispatcher : public MouseLockDispatcher {
 WebMouseEvent WebMouseEventFromGestureEvent(const WebGestureEvent& gesture) {
   WebMouseEvent mouse;
 
+  // Only convert touch screen gesture events, do not convert
+  // touchpad/mouse wheel gesture events. (crbug.com/620974)
+  if (gesture.sourceDevice != blink::WebGestureDeviceTouchscreen)
+    return mouse;
+
   switch (gesture.type) {
     case WebInputEvent::GestureScrollBegin:
       mouse.type = WebInputEvent::MouseDown;
       break;
-
     case WebInputEvent::GestureScrollUpdate:
       mouse.type = WebInputEvent::MouseMove;
       break;
-
     case WebInputEvent::GestureFlingStart:
-      if (gesture.sourceDevice == blink::WebGestureDeviceTouchscreen) {
-        // A scroll gesture on the touchscreen may end with a GestureScrollEnd
-        // when there is no velocity, or a GestureFlingStart when it has a
-        // velocity. In both cases, it should end the drag that was initiated by
-        // the GestureScrollBegin (and subsequent GestureScrollUpdate) events.
-        mouse.type = WebInputEvent::MouseUp;
-        break;
-      } else {
-        return mouse;
-      }
+      // A scroll gesture on the touchscreen may end with a GestureScrollEnd
+      // when there is no velocity, or a GestureFlingStart when it has a
+      // velocity. In both cases, it should end the drag that was initiated by
+      // the GestureScrollBegin (and subsequent GestureScrollUpdate) events.
+      mouse.type = WebInputEvent::MouseUp;
     case WebInputEvent::GestureScrollEnd:
       mouse.type = WebInputEvent::MouseUp;
       break;
-
     default:
-      break;
+      return mouse;
   }
 
-  if (mouse.type == WebInputEvent::Undefined)
-    return mouse;
-
   mouse.timeStampSeconds = gesture.timeStampSeconds;
   mouse.modifiers = gesture.modifiers | WebInputEvent::LeftButtonDown;
   mouse.button = WebMouseEvent::ButtonLeft;