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

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

Index: third_party/WebKit/Source/core/html/shadow/MediaControlElements.cpp
diff --git a/third_party/WebKit/Source/core/html/shadow/MediaControlElements.cpp b/third_party/WebKit/Source/core/html/shadow/MediaControlElements.cpp
index 36ef45117fe63fa5a41b48feb7d9b07465783d47..e76fa538b58fbedf92501b749bc467c85e41b308 100644
--- a/third_party/WebKit/Source/core/html/shadow/MediaControlElements.cpp
+++ b/third_party/WebKit/Source/core/html/shadow/MediaControlElements.cpp
@@ -35,6 +35,7 @@
 #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"
@@ -284,6 +285,12 @@ PassRefPtrWillBeRawPtr<MediaControlPlayButtonElement> MediaControlPlayButtonElem
 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();