Add NULL check of ExecutionContext in ServiceWorkerContainer

Source/modules/serviceworkers/ServiceWorkerContainer.cpp

Index: Source/modules/serviceworkers/ServiceWorkerContainer.cpp
diff --git a/Source/modules/serviceworkers/ServiceWorkerContainer.cpp b/Source/modules/serviceworkers/ServiceWorkerContainer.cpp
index 612d37b84959a9cb12573e8e280c148853c39798..4c7d6684f6bd67128e83460171c0d329f8915563 100644
--- a/Source/modules/serviceworkers/ServiceWorkerContainer.cpp
+++ b/Source/modules/serviceworkers/ServiceWorkerContainer.cpp
@@ -134,6 +134,10 @@ ScriptPromise ServiceWorkerContainer::registerServiceWorker(ScriptState* scriptS
     }
 
     ExecutionContext* executionContext = scriptState->executionContext();
+    // FIXME: May be null due to worker termination: http://crbug.com/413518.
+    if (!executionContext)
+        return ScriptPromise();
+
     RefPtr<SecurityOrigin> documentOrigin = executionContext->securityOrigin();
     String errorMessage;
     if (!executionContext->isPrivilegedContext(errorMessage)) {
@@ -193,6 +197,10 @@ ScriptPromise ServiceWorkerContainer::getRegistration(ScriptState* scriptState,
     }
 
     ExecutionContext* executionContext = scriptState->executionContext();
+    // FIXME: May be null due to worker termination: http://crbug.com/413518.
+    if (!executionContext)
+        return ScriptPromise();
+
     RefPtr<SecurityOrigin> documentOrigin = executionContext->securityOrigin();
     String errorMessage;
     if (!executionContext->isPrivilegedContext(errorMessage)) {