EME: Improve promise lifetime

third_party/WebKit/Source/modules/encryptedmedia/MediaKeySystemAccess.cpp

 // Copyright 2014 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "modules/encryptedmedia/MediaKeySystemAccess.h"
 
 #include "bindings/core/v8/ScriptPromiseResolver.h"
 #include "bindings/core/v8/ScriptState.h"
 #include "core/dom/DOMException.h"
 #include "core/dom/Document.h"
@@ skipping 27 matching lines @@
       ScriptState* scriptState,
       const WebVector<WebEncryptedMediaSessionType>& supportedSessionTypes)
       : ContentDecryptionModuleResultPromise(scriptState),
         m_supportedSessionTypes(supportedSessionTypes) {}
 
   ~NewCdmResultPromise() override {}
 
   // ContentDecryptionModuleResult implementation.
   void completeWithContentDecryptionModule(
       WebContentDecryptionModule* cdm) override {
     // NOTE: Continued from step 2.8 of createMediaKeys().

[xhwang, 2016/10/13 19:29:59]

empty line here since this is not specific to l.49-50?

[jrummell, 2016/10/14 00:03:32]

Done.

+    if (!isValidToFulfillPromise())
+      return;

[xhwang, 2016/10/13 19:29:59]

ditto

[jrummell, 2016/10/14 00:03:32]

We don't want to create the MediaKeys object if we don't need it.

+
     // 2.9. Let media keys be a new MediaKeys object.
     MediaKeys* mediaKeys = MediaKeys::create(
         getExecutionContext(), m_supportedSessionTypes, wrapUnique(cdm));
 
     // 2.10. Resolve promise with media keys.
     resolve(mediaKeys);
   }
 
  private:
   WebVector<WebEncryptedMediaSessionType> m_supportedSessionTypes;
@@ skipping 101 matching lines @@
   //     (Done if completeWithException() called).
   m_access->createContentDecryptionModule(helper->result());
 
   // 3. Return promise.
   return promise;
 }
 
 DEFINE_TRACE(MediaKeySystemAccess) {}
 
 }  // namespace blink