HeadlessWebContentsImpl::RenderViewReady can be called many times

We incorrectly assumed it was called only once.  This patch fixes that
assumption.

Change-Id: I9d8e624634260ca1e352d9419e84b52e64e627a4
Reviewed-on: https://chromium-review.googlesource.com/921082
Commit-Queue: Alex Clarke <alexclarke@chromium.org>
Reviewed-by: Alexander Timin <altimin@chromium.org>
Cr-Commit-Position: refs/heads/master@{#537282}

headless/lib/browser/headless_web_contents_impl.cc

@@ -414,8 +414,13 @@ void HeadlessWebContentsImpl::RenderFrameDeleted(
 void HeadlessWebContentsImpl::RenderViewReady() {
   DCHECK(web_contents()->GetMainFrame()->IsRenderFrameLive());
 
+  if (devtools_target_ready_notification_sent_)
+    return;
+
   for (auto& observer : observers_)
     observer.DevToolsTargetReady();
+
+  devtools_target_ready_notification_sent_ = true;
 }
 
 int HeadlessWebContentsImpl::GetMainFrameRenderProcessId() const {

headless/lib/browser/headless_web_contents_impl.h

@@ -195,6 +195,7 @@ class HEADLESS_EXPORT HeadlessWebContentsImpl
   scoped_refptr<content::DevToolsAgentHost> agent_host_;
   std::list<MojoService> mojo_services_;
   bool inject_mojo_services_into_isolated_world_;
+  bool devtools_target_ready_notification_sent_ = false;
 
   HeadlessBrowserContextImpl* browser_context_;      // Not owned.
   // TODO(alexclarke): With OOPIF there may be more than one renderer, we need