[webcrypto] Make it safe to delete WebCryptoResult from any thread.

Source/modules/crypto/CryptoResultImpl.h

 /*
  * Copyright (C) 2013 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:
  *
  *     * Redistributions of source code must retain the above copyright
  * notice, this list of conditions and the following disclaimer.
  *     * Redistributions in binary form must reproduce the above
@@ skipping 14 matching lines @@
  * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
  * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
  * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
  * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
  */
 
 #ifndef CryptoResultImpl_h
 #define CryptoResultImpl_h
 
 #include "bindings/v8/ScriptPromise.h"
-#include "bindings/v8/ScriptPromiseResolverWithContext.h"
-#include "core/dom/ContextLifecycleObserver.h"
 #include "platform/CryptoResult.h"
 #include "public/platform/WebCrypto.h"
-#include "wtf/Assertions.h"
 #include "wtf/Forward.h"
-#include "wtf/Threading.h"
+#include "wtf/WeakPtr.h"
 
 namespace WebCore {
 
 // Wrapper around a Promise to notify completion of the crypto operation.
-// Platform cannot know about Promises which are declared in bindings.
-class CryptoResultImpl FINAL : public CryptoResult, public ContextLifecycleObserver {
+//
+// The thread on which CryptoResultImpl was created on is referred to as the
+// "origin thread".
+//
+//  * At creation time there must be an active ExecutionContext.
+//  * The CryptoResult interface must only be called from the origin thread.
+//  * addref() and deref() can be called from any thread.
+//  * One of the completeWith***() functions must be called, or the
+//    PromiseState will be leaked until the ExecutionContext is destroyed.
+class CryptoResultImpl FINAL : public CryptoResult {
 public:
     ~CryptoResultImpl();
 
     static PassRefPtr<CryptoResultImpl> create();
 
     virtual void completeWithError() OVERRIDE;
     virtual void completeWithError(const blink::WebString&) OVERRIDE;
     virtual void completeWithBuffer(const blink::WebArrayBuffer&) OVERRIDE;
     virtual void completeWithBoolean(bool) OVERRIDE;
     virtual void completeWithKey(const blink::WebCryptoKey&) OVERRIDE;
     virtual void completeWithKeyPair(const blink::WebCryptoKey& publicKey, const blink::WebCryptoKey& privateKey) OVERRIDE;
 
-    ScriptPromise promise() { return m_promiseResolver->promise(); }
+    // It is only valid to call this before completion.
+    ScriptPromise promise();
 
 private:
-    CryptoResultImpl(ExecutionContext*);
-    void finish();
-    void CheckValidThread() const;
+    explicit CryptoResultImpl(ExecutionContext*);
 
-    // Override from ContextLifecycleObserver
-    virtual void contextDestroyed() OVERRIDE;
-
-    // Returns true if the ExecutionContext is still alive and running.
-    bool canCompletePromise() const;
-
-    void clearPromiseResolver();
-
-    RefPtr<ScriptPromiseResolverWithContext> m_promiseResolver;
-
-#if !ASSERT_DISABLED
-    ThreadIdentifier m_owningThread;
-    bool m_finished;
-#endif
+    class PromiseState;
+    WeakPtr<PromiseState> m_promiseState;
 };
 
 } // namespace WebCore
 
 #endif