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

content/child/webcrypto/shared_crypto.h

Index: content/child/webcrypto/shared_crypto.h
diff --git a/content/child/webcrypto/shared_crypto.h b/content/child/webcrypto/shared_crypto.h
index 3af025f000cbb397423af945859223ac3e0a99e7..1e5b50773a1fa58c23b1d6cd588959419d493865 100644
--- a/content/child/webcrypto/shared_crypto.h
+++ b/content/child/webcrypto/shared_crypto.h
@@ -21,7 +21,8 @@ namespace webcrypto {
 class CryptoData;
 class Status;
 
-// Do one-time initialization. It is safe to call this multiple times.
+// Do lazy initialization. It should be safe to call this multiple times and
+// from concurrent threads.

[Ryan Sleevi, 2014/05/13 05:47:20]

lazy vs one-time is an artifact of how it's used, not what it does. The original
comment was clearer in this respect

// Do one-time initialization. It is safe to call this multiple times and from
concurrent threads.

[eroman, 2014/05/13 18:27:15]

Changed back to original comment, but with a mention that it can be called
concurrently.

 CONTENT_EXPORT void Init();
 
 // The functions exported by shared_crypto.h provide a common entry point for