[webcrypto] Fix a race in BlinkPlatformImpl::crypto(), by using eager initilization of WebCryptoImpl

content/child/webcrypto/shared_crypto.h

 // 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.
 
 #ifndef CONTENT_CHILD_WEBCRYPTO_SHARED_CRYPTO_H_
 #define CONTENT_CHILD_WEBCRYPTO_SHARED_CRYPTO_H_
 
 #include <vector>
 
 #include "base/basictypes.h"
 #include "base/compiler_specific.h"
 #include "base/memory/scoped_ptr.h"
 #include "content/common/content_export.h"
 #include "third_party/WebKit/public/platform/WebCrypto.h"
 #include "third_party/WebKit/public/platform/WebCryptoAlgorithmParams.h"
 
 namespace content {
 
 namespace webcrypto {
 
 class CryptoData;
 class Status;
 
 // Do one-time initialization. It is safe to call this multiple times.
+// May be called concurrently from multiple threads.
 CONTENT_EXPORT void Init();
 
 // The functions exported by shared_crypto.h provide a common entry point for
 // synchronous crypto operations.
 //
 // Here is how the layer cake looks.
 //
 //              Blink
 //                |
 //  ==============|==========================
@@ skipping 122 matching lines @@
     bool extractable,
     blink::WebCryptoKeyUsageMask usage_mask,
     const CryptoData& key_data,
     blink::WebCryptoKey* key);
 
 }  // namespace webcrypto
 
 }  // namespace content
 
 #endif  // CONTENT_CHILD_WEBCRYPTO_SHARED_CRYPTO_H_