Improve HTMLMediaElement::currentTime()

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

Index: third_party/WebKit/Source/core/html/HTMLMediaElement.h
diff --git a/third_party/WebKit/Source/core/html/HTMLMediaElement.h b/third_party/WebKit/Source/core/html/HTMLMediaElement.h
index 8050c4050f996bd8d70c4ea07ff7f4da8690ce60..1167d6fa56b5b24d88871e0863a53de15943e05c 100644
--- a/third_party/WebKit/Source/core/html/HTMLMediaElement.h
+++ b/third_party/WebKit/Source/core/html/HTMLMediaElement.h
@@ -465,8 +465,12 @@ class CORE_EXPORT HTMLMediaElement : public HTMLElement,
   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();
@@ -606,9 +610,11 @@ class CORE_EXPORT HTMLMediaElement : public HTMLElement,
 
   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;