Use a mock implementation of Platform::crypto() for layout tests.

content/renderer/renderer_webkitplatformsupport_impl.cc

Index: content/renderer/renderer_webkitplatformsupport_impl.cc
diff --git a/content/renderer/renderer_webkitplatformsupport_impl.cc b/content/renderer/renderer_webkitplatformsupport_impl.cc
index 211c567114cbfd638a28ed9185a84cba2ffdb8f2..5a868cea41b4c6bf83be0e7d2390e6a635050ead 100644
--- a/content/renderer/renderer_webkitplatformsupport_impl.cc
+++ b/content/renderer/renderer_webkitplatformsupport_impl.cc
@@ -1137,6 +1137,12 @@ void RendererWebKitPlatformSupportImpl::SetMockDeviceMotionDataForTesting(
 //------------------------------------------------------------------------------
 
 WebKit::WebCrypto* RendererWebKitPlatformSupportImpl::crypto() {
+  // Use a mock implementation for testing in-progress work.
+  WebKit::WebCrypto* crypto =
+      GetContentClient()->renderer()->OverrideWebCrypto();
+  if (crypto)
+    return crypto;
+
   if (!web_crypto_)
     web_crypto_.reset(new WebCryptoImpl());
   return web_crypto_.get();