Move crypto_helpers from sync to base

ppapi/shared_impl/crypto_impl.cc

Index: ppapi/shared_impl/crypto_impl.cc
diff --git a/ppapi/shared_impl/crypto_impl.cc b/ppapi/shared_impl/crypto_impl.cc
index 6295bb2274138a588463ecf87ed0ce0f513440be..f8e4aa27e68e48a3bf2da31b9d8811f78d859954 100644
--- a/ppapi/shared_impl/crypto_impl.cc
+++ b/ppapi/shared_impl/crypto_impl.cc
@@ -11,14 +11,7 @@ namespace shared_impl {
 
 // static
 void CryptoImpl::GetRandomBytes(char* buffer, uint32_t num_bytes) {
-  // Note: this is a copy of WebKitClientImpl::cryptographicallyRandomValues.
-  uint64 bytes = 0;
-  for (uint32_t i = 0; i < num_bytes; ++i) {
-    uint32_t offset = i % sizeof(bytes);
-    if (!offset)
-      bytes = base::RandUint64();
-    buffer[i] = reinterpret_cast<char*>(&bytes)[offset];
-  }
+  base::RandBytes(buffer, num_bytes);
 }
 
 }  // namespace shared_impl