Enable smooth transition when show/hide media remoting interstitial.

third_party/WebKit/Source/core/html/shadow/MediaRemotingInterstitial.cpp

 // Copyright 2017 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 "core/html/shadow/MediaRemotingInterstitial.h"
 
+#include "core/dom/TaskRunnerHelper.h"
 #include "core/html/HTMLImageElement.h"
 #include "core/html/HTMLVideoElement.h"
 #include "core/html/shadow/MediaRemotingElements.h"
 
+namespace {
+
+constexpr double kStyleChangeTransSeconds = 0.2;
+constexpr double kHiddenAnimationSeconds = 0.3;
+
+}  // namespace
+
 namespace blink {
 
 MediaRemotingInterstitial::MediaRemotingInterstitial(
     HTMLVideoElement& videoElement)
     : HTMLDivElement(videoElement.GetDocument()),
+      is_shown_(false),
+      toggle_insterstitial_timer_(
+          TaskRunnerHelper::Get(TaskType::kUnthrottled,
+                                &videoElement.GetDocument()),
+          this,
+          &MediaRemotingInterstitial::ToggleInterstitialTimerFired),
       video_element_(&videoElement) {
   SetShadowPseudoId(AtomicString("-internal-media-remoting-interstitial"));
   background_image_ = HTMLImageElement::Create(videoElement.GetDocument());
   background_image_->SetShadowPseudoId(
       AtomicString("-internal-media-remoting-background-image"));
   background_image_->SetSrc(videoElement.getAttribute(HTMLNames::posterAttr));
   AppendChild(background_image_);
 
   cast_icon_ = new MediaRemotingCastIconElement(*this);
   AppendChild(cast_icon_);
 
   cast_text_message_ = new MediaRemotingCastMessageElement(*this);
   AppendChild(cast_text_message_);
 
   exit_button_ = new MediaRemotingExitButtonElement(*this);
   AppendChild(exit_button_);
 }
 
 void MediaRemotingInterstitial::Show() {
+  if (is_shown_ && toggle_insterstitial_timer_.IsActive())

[mlamouri (slow - plz ping), 2017/04/19 16:17:19]

Why do you check if the timer is active? Actually, do we expect this to be
called when the interstitial is showing?

[xjz, 2017/04/19 17:11:19]

Done. Yes, the timer could be active. For example, start remoting immediately
after stop remoting. But you are right, we should not expect this to be called
when |is_shown| is true. Add DCHECK.

+    return;
+  if (toggle_insterstitial_timer_.IsActive())
+    toggle_insterstitial_timer_.Stop();
+  is_shown_ = true;
   RemoveInlineStyleProperty(CSSPropertyDisplay);
-  exit_button_->OnShown();
+  toggle_insterstitial_timer_.StartOneShot(kStyleChangeTransSeconds,
+                                           BLINK_FROM_HERE);
 }
 
 void MediaRemotingInterstitial::Hide() {
-  SetInlineStyleProperty(CSSPropertyDisplay, CSSValueNone);
+  if (!is_shown_ && toggle_insterstitial_timer_.IsActive())
+    return;
+  if (toggle_insterstitial_timer_.IsActive())
+    toggle_insterstitial_timer_.Stop();
+  is_shown_ = false;
   exit_button_->OnHidden();
+  SetInlineStyleProperty(CSSPropertyOpacity, 0,
+                         CSSPrimitiveValue::UnitType::kNumber);
+  toggle_insterstitial_timer_.StartOneShot(kHiddenAnimationSeconds,
+                                           BLINK_FROM_HERE);
+}
+
+void MediaRemotingInterstitial::ToggleInterstitialTimerFired(TimerBase*) {
+  toggle_insterstitial_timer_.Stop();
+  if (is_shown_) {
+    SetInlineStyleProperty(CSSPropertyOpacity, 1,
+                           CSSPrimitiveValue::UnitType::kNumber);
+    exit_button_->OnShown();

[mlamouri (slow - plz ping), 2017/04/19 16:17:19]

Why are we not being consistent with onShown and onHidden?

[xjz, 2017/04/19 17:11:19]

The initial thought was call onHidden() first to stop listening the mouse events
when remoting stops. And call OnShown() after the interstial is stably shown.
But after a second thought, I agree that it should be OK to make the calls
consistent, which is more readable and easier for maintenance.

+  } else {
+    SetInlineStyleProperty(CSSPropertyDisplay, CSSValueNone);
+  }
+}
+
+void MediaRemotingInterstitial::DidMoveToNewDocument(Document& old_document) {
+  toggle_insterstitial_timer_.MoveToNewTaskRunner(
+      TaskRunnerHelper::Get(TaskType::kUnthrottled, &GetDocument()));
+
+  HTMLDivElement::DidMoveToNewDocument(old_document);
 }
 
 void MediaRemotingInterstitial::OnPosterImageChanged() {
   background_image_->SetSrc(
       GetVideoElement().getAttribute(HTMLNames::posterAttr));
 }
 
 DEFINE_TRACE(MediaRemotingInterstitial) {
   visitor->Trace(video_element_);
   visitor->Trace(background_image_);
   visitor->Trace(exit_button_);
   visitor->Trace(cast_icon_);
   visitor->Trace(cast_text_message_);
   HTMLDivElement::Trace(visitor);
 }
 
 }  // namespace blink