EME: Improve promise lifetime

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

Index: third_party/WebKit/Source/modules/encryptedmedia/ContentDecryptionModuleResultPromise.cpp
diff --git a/third_party/WebKit/Source/modules/encryptedmedia/ContentDecryptionModuleResultPromise.cpp b/third_party/WebKit/Source/modules/encryptedmedia/ContentDecryptionModuleResultPromise.cpp
index 58b35116e66ac7d09d376be848413d8994f3eb3a..93e50d4ecb51d2d97eaf08e759892405006db342 100644
--- a/third_party/WebKit/Source/modules/encryptedmedia/ContentDecryptionModuleResultPromise.cpp
+++ b/third_party/WebKit/Source/modules/encryptedmedia/ContentDecryptionModuleResultPromise.cpp
@@ -66,6 +66,9 @@ void ContentDecryptionModuleResultPromise::completeWithError(
     WebContentDecryptionModuleException exceptionCode,
     unsigned long systemCode,
     const WebString& errorMessage) {
+  if (!isValidToFulfillPromise())
+    return;
+
   // Non-zero |systemCode| is appended to the |errorMessage|. If the
   // |errorMessage| is empty, we'll report "Rejected with system code
   // (systemCode)".
@@ -87,24 +90,8 @@ ScriptPromise ContentDecryptionModuleResultPromise::promise() {
 
 void ContentDecryptionModuleResultPromise::reject(ExceptionCode code,
                                                   const String& errorMessage) {
-  // Reject the promise asynchronously. This avoids problems when gc is
-  // destroying objects that result in unfulfilled promises being rejected.
-  // (Resolving promises is still done synchronously as there may be events
-  // already posted that need to happen only after the promise is resolved.)
-  // TODO(jrummell): Make resolving a promise asynchronous as well (including
-  // making sure events still happen after the promise is resolved).
-  if (getExecutionContext()) {
-    getExecutionContext()->postTask(
-        BLINK_FROM_HERE,
-        createSameThreadTask(
-            &ContentDecryptionModuleResultPromise::rejectInternal,
-            wrapPersistent(this), code, errorMessage));
-  }
-}
+  DCHECK(isValidToFulfillPromise());
 
-void ContentDecryptionModuleResultPromise::rejectInternal(
-    ExceptionCode code,
-    const String& errorMessage) {
   m_resolver->reject(DOMException::create(code, errorMessage));
   m_resolver.clear();
 }
@@ -114,6 +101,12 @@ ExecutionContext* ContentDecryptionModuleResultPromise::getExecutionContext()
   return m_resolver->getExecutionContext();
 }
 
+bool ContentDecryptionModuleResultPromise::isValidToFulfillPromise() {
+  // getExecutionContext() is no longer valid once the context is destroyed.
+  return getExecutionContext() &&
+         !getExecutionContext()->activeDOMObjectsAreStopped();

[haraken, 2016/10/14 00:48:41]

Add a comment about why we need to check
getExecutionContext()->activeDOMObjectsAreStopped().

[jrummell, 2016/10/14 02:13:30]

Done.

+}
+
 DEFINE_TRACE(ContentDecryptionModuleResultPromise) {
   visitor->trace(m_resolver);
   ContentDecryptionModuleResult::trace(visitor);