Allow play/pause on default controls to clear media errors.

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

 /*
  * Copyright (C) 2008, 2009, 2010, 2011 Apple Inc. All rights reserved.
  * Copyright (C) 2012 Google 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.
@@ skipping 17 matching lines @@
  */
 
 #include "core/html/shadow/MediaControlElements.h"
 
 #include "bindings/core/v8/ExceptionStatePlaceholder.h"
 #include "core/InputTypeNames.h"
 #include "core/dom/ClientRect.h"
 #include "core/dom/shadow/ShadowRoot.h"
 #include "core/events/MouseEvent.h"
 #include "core/frame/LocalFrame.h"
+#include "core/html/HTMLMediaSource.h"
 #include "core/html/HTMLVideoElement.h"
 #include "core/html/TimeRanges.h"
 #include "core/html/shadow/MediaControls.h"
 #include "core/input/EventHandler.h"
 #include "core/layout/LayoutTheme.h"
 #include "core/layout/LayoutVideo.h"
 #include "core/layout/api/LayoutSliderItem.h"
 #include "platform/Histogram.h"
 #include "platform/RuntimeEnabledFeatures.h"
 
@@ skipping 229 matching lines @@
     RefPtrWillBeRawPtr<MediaControlPlayButtonElement> button = adoptRefWillBeNoop(new MediaControlPlayButtonElement(mediaControls));
     button->ensureUserAgentShadowRoot();
     button->setType(InputTypeNames::button);
     button->setShadowPseudoId(AtomicString("-webkit-media-controls-play-button", AtomicString::ConstructFromLiteral));
     return button.release();
 }
 
 void MediaControlPlayButtonElement::defaultEventHandler(Event* event)
 {
     if (event->type() == EventTypeNames::click) {
+        // Allow play attempts for plain src= media to force a reload in the error state. This allows potential
+        // recovery for transient network and decoder resource issues.
+        const String& url = mediaElement().currentSrc().getString();
+        if (mediaElement().error() && !HTMLMediaElement::isMediaStreamURL(url) && !HTMLMediaSource::lookup(url))

[wolenetz, 2016/03/24 23:05:04]

A web app could have explicitly revoked the MediaSource objectURL by this time.
So this logic could mistake an MSE-src'ed mediaElement() as a plain src
mediaElement(). We're luckily protected by Chrome's current
HTMLMediaElement::load() path, which checks the registry each time:

1) If the element still had an attached mediasource, it's closed and forgotten
by the element. (as part of either the error noneSupported() path, and certainly
as part of invokeLoadAlgorithm()'s call to  resetMediaPlayerAndMediaSource().
2) Then the MSE object is [re-]attached. Importantly, Blink uses the same
registry lookup to see if it's indeed an MSE-src'ed element as this line in this
CL.

The only reason I thought I was luckily getting MSE to work was that my simple
MSE player had not canceled the 'onsourceopen' event handler, which was re-fired
upon the play later.

I'm not so clear that the MSE and HTML specs match Blink's implementation that
detaches and re-attaches MSE as part of load(), but it does help protect against
some weirdness.

[philipj_slow, 2016/03/29 13:24:15]

Maybe just gate this on KURL::protocolIsInHTTPFamily()? Are there any other
protocols where we expect that trying again would make a difference?

[DaleCurtis, 2016/03/29 21:41:14]

Depending on the failure type data/blob URLs may have transient errors as well,
so I'd prefer to limit this only to situations we know won't work for
consistency.

Matt, I don't really follow your comment. The load() called here is synchronous,
the result of HTMLMediaSource::Lookup() in this code and within load() will
return the same value. Can you elaborate more on what your concern is here?

+            mediaElement().load();
+
         mediaElement().togglePlayState();
         updateDisplayType();
         event->setDefaultHandled();
     }
     HTMLInputElement::defaultEventHandler(event);
 }
 
 void MediaControlPlayButtonElement::updateDisplayType()
 {
     setDisplayType(mediaElement().paused() ? MediaPlayButton : MediaPauseButton);
@@ skipping 352 matching lines @@
 }
 
 PassRefPtrWillBeRawPtr<MediaControlCurrentTimeDisplayElement> MediaControlCurrentTimeDisplayElement::create(MediaControls& mediaControls)
 {
     RefPtrWillBeRawPtr<MediaControlCurrentTimeDisplayElement> element = adoptRefWillBeNoop(new MediaControlCurrentTimeDisplayElement(mediaControls));
     element->setShadowPseudoId(AtomicString("-webkit-media-controls-current-time-display", AtomicString::ConstructFromLiteral));
     return element.release();
 }
 
 } // namespace blink