Use explicit WebString <-> string conversion methods for workers

content/child/service_worker/web_service_worker_impl.cc

Index: content/child/service_worker/web_service_worker_impl.cc
diff --git a/content/child/service_worker/web_service_worker_impl.cc b/content/child/service_worker/web_service_worker_impl.cc
index cdbb0b0462df3a1c52dc3975f70b70b265d5c0e1..947359eb70a9e7f794c2934d61a3ffa0a60af94c 100644
--- a/content/child/service_worker/web_service_worker_impl.cc
+++ b/content/child/service_worker/web_service_worker_impl.cc
@@ -117,10 +117,9 @@ void WebServiceWorkerImpl::postMessage(
       base::Bind(&SendPostMessageToWorkerOnMainThread,
                  base::RetainedRef(thread_safe_sender_),
                  handle_ref_->handle_id(), provider_impl->provider_id(),
-                 // We cast WebString to string16 before crossing
+                 // We convert WebString to string16 before crossing
                  // threads for thread-safety.
-                 static_cast<base::string16>(message),
-                 url::Origin(source_origin),
+                 message.utf16(), url::Origin(source_origin),

[falken, 2016/12/26 01:26:20]

Do you know why this IPC should be a string16 and not just std::string?

                  base::Passed(base::WrapUnique(channels))));
 }