Measure usage of createObjectURL and srcObject

third_party/WebKit/Source/modules/mediasource/URLMediaSource.cpp

 /*
  * Copyright (C) 2013 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:
  *
  *     * Redistributions of source code must retain the above copyright
  * notice, this list of conditions and the following disclaimer.
  *     * Redistributions in binary form must reproduce the above
@@ skipping 13 matching lines @@
  * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
  * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
  * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
  * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
  * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
  */
 
 #include "modules/mediasource/URLMediaSource.h"
 
 #include "core/dom/DOMURL.h"
+#include "core/frame/UseCounter.h"
 #include "modules/mediasource/MediaSource.h"
 
 namespace blink {
 
 String URLMediaSource::createObjectURL(ExecutionContext* executionContext, MediaSource* source)
 {
     // Since WebWorkers cannot obtain MediaSource objects, we should be on the main thread.
     DCHECK(isMainThread());
+    DCHECK(executionContext);

[hta - Chromium, 2016/09/29 13:46:33]

Since you're now DCHECKing (and, I think, crashing in production) something that
used to return an empty string, this needs review to figure out if it matters.

[foolip, 2016/09/29 14:54:45]

executionContext and source cannot be null here, as in
URLFileAPI::createObjectURL.

+    DCHECK(source);
 
-    if (!executionContext)
-        return String();
+    UseCounter::count(executionContext, UseCounter::CreateObjectURLMediaSource);
     return DOMURL::createPublicURL(executionContext, source);
 }
 
 } // namespace blink