[DevTools] Fix frontend host race and assert.

content/renderer/devtools/devtools_client.cc

Index: content/renderer/devtools/devtools_client.cc
diff --git a/content/renderer/devtools/devtools_client.cc b/content/renderer/devtools/devtools_client.cc
index b19516b3d149f4ed51711e4c8ffa52d27558ea41..3f9612938248ba0dffbf37410fdb090d88c1f9cd 100644
--- a/content/renderer/devtools/devtools_client.cc
+++ b/content/renderer/devtools/devtools_client.cc
@@ -26,12 +26,9 @@ DevToolsClient::DevToolsClient(
     RenderFrame* main_render_frame,
     const std::string& compatibility_script)
     : RenderFrameObserver(main_render_frame),
-      compatibility_script_(compatibility_script) {
-  const base::CommandLine& command_line =
-      *base::CommandLine::ForCurrentProcess();
-  web_tools_frontend_.reset(WebDevToolsFrontend::create(
-      main_render_frame->GetRenderView()->GetWebView(), this,
-      base::ASCIIToUTF16(command_line.GetSwitchValueASCII(switches::kLang))));
+      compatibility_script_(compatibility_script),
+      web_tools_frontend_(
+          WebDevToolsFrontend::create(main_render_frame->GetWebFrame(), this)) {
 }
 
 DevToolsClient::~DevToolsClient() {