MD Buttons: Don't add layers for hidden -> hidden transitions.

ui/views/animation/ink_drop_impl.cc

 // Copyright 2015 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.
 
 #include "ui/views/animation/ink_drop_impl.h"
 
 #include "base/auto_reset.h"
 #include "base/timer/timer.h"
 #include "ui/compositor/layer.h"
 #include "ui/views/animation/ink_drop_highlight.h"
@@ skipping 56 matching lines @@
   DestroyInkDropHighlight();
 }
 
 InkDropState InkDropImpl::GetTargetInkDropState() const {
   if (!ink_drop_ripple_)
     return InkDropState::HIDDEN;
   return ink_drop_ripple_->target_ink_drop_state();
 }
 
 void InkDropImpl::AnimateToState(InkDropState ink_drop_state) {
+  // Never animate hidden -> hidden, since that will add layers which may never
+  // be needed. Other same-state transitions may restart animations.
+  if (ink_drop_state == InkDropState::HIDDEN &&
+      GetTargetInkDropState() == InkDropState::HIDDEN)
+    return;
+
   DestroyHiddenTargetedAnimations();
   if (!ink_drop_ripple_)
     CreateInkDropRipple();
 
   if (ink_drop_ripple_->OverridesHighlight()) {
     // When deactivating and the host is focused, snap back to the highlight
     // state. (In the case of highlighting due to hover, we'll animate the
     // highlight back in after a delay.)
     if (ink_drop_state == views::InkDropState::DEACTIVATED && is_focused_) {
       ink_drop_ripple_->HideImmediately();
@@ skipping 178 matching lines @@
 }
 
 void InkDropImpl::HighlightAfterRippleTimerFired() {
   SetHighlight(true, base::TimeDelta::FromMilliseconds(
                          kHighlightFadeInAfterRippleDurationMs),
                true);
   highlight_after_ripple_timer_.reset();
 }
 
 }  // namespace views