[WIP] Allow scroll events to permanently change the default gesture handler in RootView

ui/views/controls/button/custom_button.cc

Index: ui/views/controls/button/custom_button.cc
diff --git a/ui/views/controls/button/custom_button.cc b/ui/views/controls/button/custom_button.cc
index 1b5d1e82ffbd705b332ed9ce3057a60a8d2da995..ef2c7eb0f8237db223cbdcfc4a95b256d208ea28 100644
--- a/ui/views/controls/button/custom_button.cc
+++ b/ui/views/controls/button/custom_button.cc
@@ -228,12 +228,9 @@ void CustomButton::OnGestureEvent(ui::GestureEvent* event) {
   }
 
   if (event->type() == ui::ET_GESTURE_TAP && IsTriggerableEvent(*event)) {
-    // Set the button state to hot and start the animation fully faded in. The
-    // GESTURE_END event issued immediately after will set the state to
-    // STATE_NORMAL beginning the fade out animation. See
-    // http://crbug.com/131184.
-    SetState(STATE_HOVERED);
-    hover_animation_->Reset(1.0);
+    // Since no hover state was shown on a tap down, do not show any
+    // hover state after a tap.
+    SetState(STATE_NORMAL);

[sadrul, 2014/07/24 19:12:13]

Does this actually cause any visual regression?

[tdanderson, 2014/07/25 17:16:10]

Yes it does. After a tap is complete we no longer see the hover state of the
button appear momentarily. But IMO it is more correct to do it this way because
the hover state is only something I'd expect to see with a visible mouse pointer
over the button.

[tdresser, 2014/07/25 17:24:20]

I'm pretty sure we do want to see the hover state briefly after a tap. It lets
the user know they did in fact hit the button.

[tdanderson, 2014/07/25 17:49:20]

My point was that the HOVERED state shouldn't appear on a tap because I'm not
actually hovering anything. You're right though that currently it does serve as
feedback for the user which seems necessary on small buttons. I am looking into
a workaround for this.

(Ideally, though, we would have a separate visual effects for "a visible pointer
is currently hovered over the button" and "the user has just clicked or tapped
the button". I don't think the current hover state should serve both functions.)

[tdanderson, 2014/07/25 18:53:02]

Looks like https://codereview.chromium.org/416343003/
can remove the GESTURE_END case with no visual regression.

     NotifyClick(*event);
     event->StopPropagation();
   } else if (event->type() == ui::ET_GESTURE_TAP_DOWN &&
@@ -242,8 +239,7 @@ void CustomButton::OnGestureEvent(ui::GestureEvent* event) {
     if (request_focus_on_press_)
       RequestFocus();
     event->StopPropagation();
-  } else if (event->type() == ui::ET_GESTURE_TAP_CANCEL ||
-             event->type() == ui::ET_GESTURE_END) {
+  } else if (event->type() == ui::ET_GESTURE_TAP_CANCEL) {
     SetState(STATE_NORMAL);
   }
   if (!event->handled())