Ink drops with touch input are redundant on Windows since the OS does something similar

ui/views/animation/ink_drop_host_view.cc

Index: ui/views/animation/ink_drop_host_view.cc
diff --git a/ui/views/animation/ink_drop_host_view.cc b/ui/views/animation/ink_drop_host_view.cc
index e6b1e424155d41e75056cdf1744fc2e7e2684fcc..6053bf70d26a9f3f903d4753620e1d9c697d28c1 100644
--- a/ui/views/animation/ink_drop_host_view.cc
+++ b/ui/views/animation/ink_drop_host_view.cc
@@ -172,6 +172,15 @@ gfx::Point InkDropHostView::GetInkDropCenterBasedOnLastEvent() const {
 
 void InkDropHostView::AnimateInkDrop(InkDropState state,
                                      const ui::LocatedEvent* event) {
+#if defined(OS_WIN)
+  if ((state == InkDropState::ACTION_PENDING ||

[sky, 2016/06/24 19:21:11]

Is there a reason why you care about the state in this case? Isn't the event
enough?

[Evan Stade, 2016/06/24 20:28:30]

I imagine this is to handle cases like if you were to press down with the mouse
then tap the view before releasing the mouse button?

I'd go for simpler code instead of trying to support a crazy use case like this,
unless the simpler code makes things look totally broken. Either way, docs would
be nice because this block is hard to grok.

[kylix_rd, 2016/06/24 20:32:18]

Only certain states or actions should be allowed to propagate when the event
source is touch (or gestures). Because Windows provides its own touch feedback
that is similar to the ink-drop feedback, it is favored. Only when the ink is
already present (from a mouse-click or focus event) should the state be
transitioned regardless of the event source.

At least that is my understanding of the requirement.

+       state == InkDropState::ALTERNATE_ACTION_PENDING ||
+       ((state == InkDropState::ACTION_TRIGGERED ||
+         state == InkDropState::ALTERNATE_ACTION_TRIGGERED) &&
+        ink_drop_->GetTargetInkDropState() == InkDropState::HIDDEN)) &&
+      event && event->IsGestureEvent())
+    return;
+#endif
   last_ripple_triggering_event_.reset(
       event ? ui::Event::Clone(*event).release()->AsLocatedEvent() : nullptr);
   ink_drop_->AnimateToState(state);