Add chromium side implementation of WebKit::WebCrypto.

content/renderer/webcrypto_impl.cc

Index: content/renderer/webcrypto_impl.cc
diff --git a/content/renderer/webcrypto_impl.cc b/content/renderer/webcrypto_impl.cc
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+// Copyright (c) 2013 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.
+
+#include "content/renderer/webcrypto_impl.h"
+
+#include "third_party/WebKit/public/platform/WebCryptoAlgorithm.h"
+
+namespace content {
+
+WebKit::WebCryptoOperation* WebCryptoImpl::digest(
+    const WebKit::WebCryptoAlgorithm& algorithm) {
+  switch (algorithm.id()) {
+    case WebKit::WebCryptoAlgorithmIdSha1:
+    case WebKit::WebCryptoAlgorithmIdSha224:
+    case WebKit::WebCryptoAlgorithmIdSha256:
+    case WebKit::WebCryptoAlgorithmIdSha384:
+    case WebKit::WebCryptoAlgorithmIdSha512:
+      // TODO(eroman): Implement.
+      return NULL;
+    default:
+      // Not a digest algorithm.
+      return NULL;
+  }
+}
+
+}  // namespace content