Media Controls: Clean up the DOM

Do not create the volume slider on the new media controls
as we don't need it. Also, avoids adding elements to the
DOM that are permanently hidden.

BUG=821961,821414

Change-Id: Ia0e334b6079450d4a3b084371629f6b6ba37176c
Reviewed-on: https://chromium-review.googlesource.com/991293
Commit-Queue: Becca Hughes <beccahughes@chromium.org>
Reviewed-by: Mounir Lamouri <mlamouri@chromium.org>
Cr-Commit-Position: refs/heads/master@{#547743}

third_party/WebKit/Source/modules/media_controls/MediaControlsImpl.cpp

@@ -155,6 +155,12 @@ bool ShouldShowFullscreenButton(const HTMLMediaElement& media_element) {
   return true;
 }
 
+void MaybeAppendChild(Element* parent, Element* child) {
+  DCHECK(parent);
+  if (child)
+    parent->AppendChild(child);
+}
+
 bool ShouldShowPictureInPictureButton(HTMLMediaElement& media_element) {
   return media_element.SupportsPictureInPicture();
 }
@@ -439,6 +445,7 @@ MediaControlsImpl* MediaControlsImpl::Create(HTMLMediaElement& media_element,
 //     |  |  <video> only, otherwise children are directly attached to parent
 //     |  +-MediaControlPlayButtonElement
 //     |  |    (-webkit-media-controls-play-button)
+//     |  |    {only present if audio only or ModernMediaControls is disabled}
 //     |  +-MediaControlCurrentTimeDisplayElement
 //     |  |    (-webkit-media-controls-current-time-display)
 //     |  +-MediaControlRemainingTimeDisplayElement
@@ -450,16 +457,20 @@ MediaControlsImpl* MediaControlsImpl::Create(HTMLMediaElement& media_element,
 //     |  |    (-webkit-media-controls-mute-button)
 //     |  +-MediaControlVolumeSliderElement
 //     |  |    (-webkit-media-controls-volume-slider)
+//     |  |    {if not ModernMediaControlsEnabled}
 //     |  +-MediaControlPictureInPictureButtonElement
 //     |  |    (-webkit-media-controls-picture-in-picture-button)
 //     |  +-MediaControlFullscreenButtonElement
 //     |  |    (-webkit-media-controls-fullscreen-button)
 //     |  +-MediaControlDownloadButtonElement
 //     |  |    (-internal-media-controls-download-button)
+//     |  |    {on the overflow menu if ModernMediaControls is enabled}
 //     |  +-MediaControlToggleClosedCaptionsButtonElement
 //     |  |    (-webkit-media-controls-toggle-closed-captions-button)
+//     |  |    {on the overflow menu if ModernMediaControls is enabled}
 //     |  +-MediaControlCastButtonElement
 //     |       (-internal-media-controls-cast-button)
+//     |       {on the overflow menu if ModernMediaControls is enabled}
 //     \-MediaControlTimelineElement
 //          (-webkit-media-controls-timeline)
 // +-MediaControlTextTrackListElement
@@ -516,9 +527,12 @@ void MediaControlsImpl::InitializeControls() {
   timeline_ = new MediaControlTimelineElement(*this);
   mute_button_ = new MediaControlMuteButtonElement(*this);
 
+  // The volume slider should be shown if we are using the legacy controls.
+  if (!IsModern()) {
     volume_slider_ = new MediaControlVolumeSliderElement(*this);
     if (PreferHiddenVolumeControls(GetDocument()))
       volume_slider_->SetIsWanted(false);
+  }
 
   // TODO(apacible): Enable for modern controls when SVG is added.
   if (RuntimeEnabledFeatures::PictureInPictureEnabled() && !IsModern() &&
@@ -585,14 +599,19 @@ void MediaControlsImpl::PopulatePanel() {
   Element* button_panel = panel_;
   if (IsModern() && MediaElement().IsHTMLVideoElement() &&
       !is_acting_as_audio_controls_) {
-    if (scrubbing_message_)
-      panel_->AppendChild(scrubbing_message_);
+    MaybeAppendChild(panel_, scrubbing_message_);
     panel_->AppendChild(overlay_play_button_);
     panel_->AppendChild(media_button_panel_);
     button_panel = media_button_panel_;
   }
 
+  // The play button should only be on the button panel if we are playing audio
+  // only or are using the legacy controls.
+  if (!IsModern() || is_acting_as_audio_controls_ ||
+      MediaElement().IsHTMLAudioElement()) {
     button_panel->AppendChild(play_button_);
+  }
+
   button_panel->AppendChild(current_time_display_);
   button_panel->AppendChild(duration_display_);
 
@@ -604,15 +623,20 @@ void MediaControlsImpl::PopulatePanel() {
   panel_->AppendChild(timeline_);
 
   button_panel->AppendChild(mute_button_);
-  button_panel->AppendChild(volume_slider_);
 
-  if (picture_in_picture_button_)
-    button_panel->AppendChild(picture_in_picture_button_);
+  MaybeAppendChild(button_panel, volume_slider_);
+  MaybeAppendChild(button_panel, picture_in_picture_button_);
 
   button_panel->AppendChild(fullscreen_button_);
+
+  // The download, cast and captions buttons should not be present on the modern
+  // controls button panel.
+  if (!IsModern()) {
     button_panel->AppendChild(download_button_);
     button_panel->AppendChild(cast_button_);
     button_panel->AppendChild(toggle_closed_captions_button_);
+  }
+
   button_panel->AppendChild(overflow_menu_);
 }
 
@@ -1367,15 +1391,17 @@ bool MediaControlsImpl::ContainsRelatedTarget(Event* event) {
 
 void MediaControlsImpl::OnVolumeChange() {
   mute_button_->UpdateDisplayType();
-  volume_slider_->SetVolume(MediaElement().muted() ? 0
-                                                   : MediaElement().volume());
 
   // Update visibility of volume controls.
   // TODO(mlamouri): it should not be part of the volumechange handling because
   // it is using audio availability as input.
   BatchedControlUpdate batch(this);
+  if (volume_slider_) {
+    volume_slider_->SetVolume(MediaElement().muted() ? 0
+                                                     : MediaElement().volume());
     volume_slider_->SetIsWanted(MediaElement().HasAudio() &&
                                 !PreferHiddenVolumeControls(GetDocument()));
+  }
   if (ShouldShowDisabledControls()) {
     mute_button_->SetIsWanted(true);
     mute_button_->setAttribute(

third_party/WebKit/Source/modules/media_controls/MediaControlsWindowEventListener.cpp

@@ -50,6 +50,22 @@ bool MediaControlsWindowEventListener::operator==(
   return this == &other;
 }
 
+void MediaControlsWindowEventListener::MaybeAddClickEventListener(
+    Element* element) {
+  if (!element)
+    return;
+
+  element->addEventListener(EventTypeNames::click, this, false);
+}
+
+void MediaControlsWindowEventListener::MaybeRemoveClickEventListener(
+    Element* element) {
+  if (!element)
+    return;
+
+  element->removeEventListener(EventTypeNames::click, this, false);
+}
+
 void MediaControlsWindowEventListener::Start() {
   if (is_active_)
     return;
@@ -74,12 +90,8 @@ void MediaControlsWindowEventListener::Start() {
                                                false);
   media_controls_->cast_button_->addEventListener(EventTypeNames::click, this,
                                                   false);
-  media_controls_->volume_slider_->addEventListener(EventTypeNames::click, this,
-                                                    false);
-  if (media_controls_->overlay_play_button_) {
-    media_controls_->overlay_play_button_->addEventListener(
-        EventTypeNames::click, this, false);
-  }
+  MaybeAddClickEventListener(media_controls_->volume_slider_);
+  MaybeAddClickEventListener(media_controls_->overlay_play_button_);
 
   is_active_ = true;
 }
@@ -109,12 +121,8 @@ void MediaControlsWindowEventListener::Stop() {
                                                   false);
   media_controls_->cast_button_->removeEventListener(EventTypeNames::click,
                                                      this, false);
-  media_controls_->volume_slider_->removeEventListener(EventTypeNames::click,
-                                                       this, false);
-  if (media_controls_->overlay_play_button_) {
-    media_controls_->overlay_play_button_->removeEventListener(
-        EventTypeNames::click, this, false);
-  }
+  MaybeRemoveClickEventListener(media_controls_->volume_slider_);
+  MaybeRemoveClickEventListener(media_controls_->overlay_play_button_);
 
   is_active_ = false;
 }

third_party/WebKit/Source/modules/media_controls/MediaControlsWindowEventListener.h

@@ -10,6 +10,7 @@
 
 namespace blink {
 
+class Element;
 class MediaControlsImpl;
 
 class MediaControlsWindowEventListener final : public EventListener {
@@ -30,6 +31,10 @@ class MediaControlsWindowEventListener final : public EventListener {
 
   void handleEvent(ExecutionContext*, Event*) override;
 
+  // Adds or removes a click event listener if the provided element is not null.
+  void MaybeAddClickEventListener(Element*);
+  void MaybeRemoveClickEventListener(Element*);
+
   Member<MediaControlsImpl> media_controls_;
   Callback callback_;
   bool is_active_;