New Public IdFromWebContents method on TabManager.

chrome/browser/memory/tab_manager.h

Index: chrome/browser/memory/tab_manager.h
diff --git a/chrome/browser/memory/tab_manager.h b/chrome/browser/memory/tab_manager.h
index fefdcd4eb3bc53bc95078c5aafdb37846752b594..9cac336b76399d0ef7998e406e3e8801cf144ecf 100644
--- a/chrome/browser/memory/tab_manager.h
+++ b/chrome/browser/memory/tab_manager.h
@@ -151,6 +151,10 @@ class TabManager : public TabStripModelObserver {
   // |second|.
   static bool CompareTabStats(const TabStats& first, const TabStats& second);
 
+  // Returns a unique ID for a WebContents. Do not cast back to a pointer, as
+  // the WebContents could be deleted if the user closed the tab.
+  static int64_t IdFromWebContents(content::WebContents* web_contents);
+
  private:
   FRIEND_TEST_ALL_PREFIXES(TabManagerTest, AutoDiscardable);
   FRIEND_TEST_ALL_PREFIXES(TabManagerTest, CanOnlyDiscardOnce);