[ServiceWorker] Stop using GetUserAgent from non-browser process

The result of ContentClient::GetUserAgent is known to be incorrect in
the renderer process, so get the value in the browser and pass it via
IPC.

Bug: 818450
Change-Id: Ia1af4c237b9d63059c634cd0bbb41ab53436b8cd
Reviewed-on: https://chromium-review.googlesource.com/c/1352119Reviewed-by: Makoto Shimazu <shimazu@chromium.org>
Reviewed-by: Kinuko Yasuda <kinuko@chromium.org>
Commit-Queue: Yutaka Hirano <yhirano@chromium.org>
Cr-Commit-Position: refs/heads/master@{#611599}

content/browser/service_worker/service_worker_version.cc

@@ -1585,6 +1585,7 @@ void ServiceWorkerVersion::StartWorkerInternal() {
   params->scope = scope_;
   params->script_url = script_url_;
   params->script_type = script_type_;
+  params->user_agent = GetContentClient()->GetUserAgent();
   params->is_installed = IsInstalled(status_);
   params->pause_after_download = pause_after_download();
 

content/common/service_worker/embedded_worker.mojom

@@ -43,6 +43,8 @@ struct EmbeddedWorkerStartParams {
   // This service worker's script type:
   // https://w3c.github.io/ServiceWorker/#dfn-type
   blink.mojom.ScriptType script_type;
+  // The string used for "user-agent" HTTP header.
+  string user_agent;
   // The id to talk with the DevTools agent for the worker.
   int32 worker_devtools_agent_route_id;
   // Unique token identifying this worker for DevTools.

content/renderer/service_worker/embedded_worker_instance_client_impl.cc

@@ -164,8 +164,7 @@ EmbeddedWorkerInstanceClientImpl::StartWorkerContext(
 
   blink::WebEmbeddedWorkerStartData start_data;
   start_data.script_url = params->script_url;
-  start_data.user_agent =
-      blink::WebString::FromUTF8(GetContentClient()->GetUserAgent());
+  start_data.user_agent = blink::WebString::FromUTF8(params->user_agent);
   start_data.script_type = params->script_type;
   start_data.wait_for_debugger_mode =
       params->wait_for_debugger