Add Page.stopLoading to devtools and --timeout switch to headless_shell

headless/lib/browser/headless_web_contents_impl.cc

Index: headless/lib/browser/headless_web_contents_impl.cc
diff --git a/headless/lib/browser/headless_web_contents_impl.cc b/headless/lib/browser/headless_web_contents_impl.cc
index dabdee17482ebde14bec6bffdc7e108068ecac94..36dfea6d389386cc3356944bc2f01cc5061ea5b2 100644
--- a/headless/lib/browser/headless_web_contents_impl.cc
+++ b/headless/lib/browser/headless_web_contents_impl.cc
@@ -204,6 +204,11 @@ void HeadlessWebContentsImpl::Close() {
   browser_context()->DestroyWebContents(this);
 }
 
+void HeadlessWebContentsImpl::Stop() {
+  DCHECK_CURRENTLY_ON(content::BrowserThread::UI);
+  web_contents_->Stop();
+}
+
 std::string HeadlessWebContentsImpl::GetDevToolsAgentHostId() {
   return agent_host_->GetId();
 }