Fixes ASan crash for an embedded Blink-in-JS component.

third_party/WebKit/Source/bindings/core/v8/V8Initializer.cpp

 /*
  * Copyright (C) 2009 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:
  * 1. Redistributions of source code must retain the above copyright
  *    notice, this list of conditions and the following disclaimer.
  * 2. Redistributions in binary form must reproduce the above copyright
  *    notice, this list of conditions and the following disclaimer in the
@@ skipping 96 matching lines @@
         }
     }
     return emptyString();
 }
 
 static void messageHandlerInMainThread(v8::Local<v8::Message> message, v8::Local<v8::Value> data)
 {
     ASSERT(isMainThread());
     v8::Isolate* isolate = v8::Isolate::GetCurrent();
 
+    if (isolate->GetEnteredContext().IsEmpty())
+        return;
+
     // If called during context initialization, there will be no entered context.
     ScriptState* scriptState = ScriptState::current(isolate);
     if (!scriptState->contextIsValid())
         return;
 
     ExecutionContext* context = scriptState->getExecutionContext();
     OwnPtr<SourceLocation> location = SourceLocation::fromMessage(isolate, message, context);
 
     AccessControlStatus accessControlStatus = NotSharableCrossOrigin;
     if (message->IsOpaque())
@@ skipping 300 matching lines @@
 
     isolate->AddMessageListener(messageHandlerInWorker);
     isolate->SetFatalErrorHandler(reportFatalErrorInWorker);
 
     uint32_t here;
     isolate->SetStackLimit(reinterpret_cast<uintptr_t>(&here - kWorkerMaxStackSize / sizeof(uint32_t*)));
     isolate->SetPromiseRejectCallback(promiseRejectHandlerInWorker);
 }
 
 } // namespace blink