[Panels] Provide a tab id for web contents in Panels.

chrome/browser/ui/panels/panel_host.cc

Index: chrome/browser/ui/panels/panel_host.cc
diff --git a/chrome/browser/ui/panels/panel_host.cc b/chrome/browser/ui/panels/panel_host.cc
index c78c12c0754bd6fcd55c106d97194b6fb55ce07f..5dd5ce44d9a15d6838a93e12f836f16f13bf3bcb 100644
--- a/chrome/browser/ui/panels/panel_host.cc
+++ b/chrome/browser/ui/panels/panel_host.cc
@@ -11,6 +11,7 @@
 #include "chrome/browser/extensions/window_controller.h"
 #include "chrome/browser/favicon/favicon_tab_helper.h"
 #include "chrome/browser/profiles/profile.h"
+#include "chrome/browser/sessions/session_tab_helper.h"
 #include "chrome/browser/ui/browser_navigator.h"
 #include "chrome/browser/ui/panels/panel.h"
 #include "chrome/browser/ui/prefs/prefs_tab_helper.h"
@@ -56,6 +57,11 @@ void PanelHost::Init(const GURL& url) {
   web_contents_->SetDelegate(this);
   content::WebContentsObserver::Observe(web_contents_.get());
 
+  // Needed to give the web contents a Tab ID.

[Dmitry Titov, 2012/09/21 01:29:42]

Could you add a motivation to this comment, so it is clear that the only reason
we need the Tab ID here is to satisfy the extension tab API, partially. And I'd
add TODO to remove this in the future.

[jennb, 2012/09/21 17:28:35]

Done. http://crbug.com/151474 created to track the future cleanup.

+  SessionTabHelper::CreateForWebContents(web_contents_.get());
+  SessionTabHelper::FromWebContents(web_contents_.get())->SetWindowID(
+      panel_->session_id());
+
   favicon_tab_helper_.reset(new FaviconTabHelper(web_contents_.get()));
   prefs_tab_helper_.reset(new PrefsTabHelper(web_contents_.get()));