Enable devtools via context menu in platform apps and popup extensions.

content/browser/debugger/render_view_devtools_agent_host.cc

Index: content/browser/debugger/render_view_devtools_agent_host.cc
diff --git a/content/browser/debugger/render_view_devtools_agent_host.cc b/content/browser/debugger/render_view_devtools_agent_host.cc
index 54e4c796bf235568cde0b974db5a4d0c985a4166..cf64e273132dcfec7a17a9e0e33a01a1e4ddc215 100644
--- a/content/browser/debugger/render_view_devtools_agent_host.cc
+++ b/content/browser/debugger/render_view_devtools_agent_host.cc
@@ -75,6 +75,15 @@ RenderViewDevToolsAgentHost::RenderViewDevToolsAgentHost(RenderViewHost* rvh)
     : content::RenderViewHostObserver(rvh),
       render_view_host_(rvh) {
   g_instances.Get()[rvh] = this;
+
+  // Notify that the view is being opened. This allows any views being debugged
+  // to do anything special they need to do to support debugging.
+  content::NotificationService::current()->Notify(
+      content::NOTIFICATION_DEVTOOLS_WINDOW_OPENING,
+      content::Source<content::BrowserContext>(
+          render_view_host_->site_instance()->GetProcess()->
+              GetBrowserContext()),
+      content::Details<RenderViewHost>(render_view_host_));
 }
 
 void RenderViewDevToolsAgentHost::SendMessageToAgent(IPC::Message* msg) {