Measure usage of createObjectURL and srcObject

third_party/WebKit/Source/modules/mediastream/URLMediaStream.cpp

Index: third_party/WebKit/Source/modules/mediastream/URLMediaStream.cpp
diff --git a/third_party/WebKit/Source/modules/mediastream/URLMediaStream.cpp b/third_party/WebKit/Source/modules/mediastream/URLMediaStream.cpp
index 8f10116f5b25c89907e2bc90f05b3842895cbf5f..2060db6aa5298c3d6524bca0e385dab3bfb97d42 100644
--- a/third_party/WebKit/Source/modules/mediastream/URLMediaStream.cpp
+++ b/third_party/WebKit/Source/modules/mediastream/URLMediaStream.cpp
@@ -31,6 +31,7 @@
 #include "modules/mediastream/URLMediaStream.h"
 
 #include "core/dom/DOMURL.h"
+#include "core/frame/UseCounter.h"
 #include "modules/mediastream/MediaStream.h"
 
 namespace blink {
@@ -39,9 +40,10 @@ String URLMediaStream::createObjectURL(ExecutionContext* executionContext, Media
 {
     // Since WebWorkers cannot obtain Stream objects, we should be on the main thread.
     DCHECK(isMainThread());
+    DCHECK(executionContext);

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

Same comment on both executionContext and stream here.

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

The stream check was needed at some point when all interface types were
implicitly nullable, as they still are if [LegacyInterfaceTypeChecking] is used.

+    DCHECK(stream);
 
-    if (!executionContext || !stream)
-        return String();
+    UseCounter::count(executionContext, UseCounter::CreateObjectURLMediaStream);
     return DOMURL::createPublicURL(executionContext, stream);
 }