Improve HTMLMediaElement::currentTime()

third_party/WebKit/Source/core/html/HTMLMediaElement.h

 /*
  * Copyright (C) 2007, 2008, 2009, 2010, 2011, 2012, 2013 Apple Inc. All rights
  * reserved.
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions
  * are met:
  * 1. Redistributions of source code must retain the above copyright
  *    notice, this list of conditions and the following disclaimer.
  * 2. Redistributions in binary form must reproduce the above copyright
@@ skipping 447 matching lines @@
   bool couldPlayIfEnoughData() const;
 
   // Generally the presence of the loop attribute should be considered to mean
   // playback has not "ended", as "ended" and "looping" are mutually exclusive.
   // See
   // https://html.spec.whatwg.org/multipage/embedded-content.html#ended-playback
   enum class LoopCondition { Included, Ignored };
   bool endedPlayback(LoopCondition = LoopCondition::Included) const;
 
   void setShouldDelayLoadEvent(bool);
-  void invalidateCachedTime();
-  void refreshCachedTime() const;
+
+  double earliestPossiblePosition() const;
+  double currentPlaybackPosition() const;
+  double officialPlaybackPosition() const;
+  void setOfficialPlaybackPosition(double) const;
+  void requireOfficialPlaybackPositionUpdate() const;
 
   void ensureMediaControls();
   void configureMediaControls();
 
   TextTrackContainer& ensureTextTrackContainer();
 
   EventDispatchHandlingState* preDispatchEventHandler(Event*) final;
 
   void changeNetworkStateFromLoadingToIdle();
 
@@ skipping 119 matching lines @@
   DeferredLoadState m_deferredLoadState;
   Timer<HTMLMediaElement> m_deferredLoadTimer;
 
   std::unique_ptr<WebMediaPlayer> m_webMediaPlayer;
   WebLayer* m_webLayer;
 
   DisplayMode m_displayMode;
 
   Member<HTMLMediaSource> m_mediaSource;
 
-  // Cached time value. Only valid when ready state is kHaveMetadata or
-  // higher, otherwise the current time is assumed to be zero.
-  mutable double m_cachedTime;
+  // Stores "official playback position", updated periodically from "current
+  // playback position". Official playback position should not change while
+  // scripts are running. See setOfficialPlaybackPosition().
+  mutable double m_officialPlaybackPosition;
+  mutable bool m_officialPlaybackPositionNeedsUpdate;

[mlamouri (slow - plz ping), 2016/10/26 15:32:54]

Why are these mutable?

[chcunningham, 2016/10/26 19:29:41]

Just like with m_cachedTime, these variables end up being updated in what is
externally thought of as a const method (currentTime()). Its ugly, but its
perhaps more ugly to remove the const from currentTime? Open to suggestions.

 
   double m_fragmentEndTime;
 
   typedef unsigned PendingActionFlags;
   PendingActionFlags m_pendingActionFlags;
 
   // FIXME: HTMLMediaElement has way too many state bits.
   bool m_lockedPendingUserGesture : 1;
   bool m_playing : 1;
   bool m_shouldDelayLoadEvent : 1;
@@ skipping 107 matching lines @@
 
 inline bool isHTMLMediaElement(const HTMLElement& element) {
   return isHTMLAudioElement(element) || isHTMLVideoElement(element);
 }
 
 DEFINE_HTMLELEMENT_TYPE_CASTS_WITH_FUNCTION(HTMLMediaElement);
 
 }  // namespace blink
 
 #endif  // HTMLMediaElement_h