New Public IdFromWebContents method on TabManager.

chrome/browser/memory/tab_manager.h

 // Copyright (c) 2012 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #ifndef CHROME_BROWSER_MEMORY_TAB_MANAGER_H_
 #define CHROME_BROWSER_MEMORY_TAB_MANAGER_H_
 
 #include <stdint.h>
 
 #include <memory>
@@ skipping 94 matching lines @@
   // Discards a tab with the given unique ID. The tab still exists in the
   // tab-strip; clicking on it will reload it. Returns null if the tab cannot
   // be found or cannot be discarded. Otherwise returns the new web_contents
   // of the discarded tab.
   content::WebContents* DiscardTabById(int64_t target_web_contents_id);
 
   // Method used by the extensions API to discard tabs. If |contents| is null,
   // discards the least important tab using DiscardTab(). Otherwise discards
   // the given contents. Returns the new web_contents or null if no tab
   // was discarded.
   content::WebContents* DiscardTabByExtension(content::WebContents* contents);

[Devlin, 2016/08/17 00:02:44]

drive-by: It might make sense to rename this method to be something like
DiscardTabWithWebContents() so that readers don't assume that either a) it
should only be used by extensions or b) it does some kind of attribution to
extensions.  I'd probably also omit the part about "used by the extensions API"
- method descriptions should typically describe the behavior rather than the
call sites (unless there's a reason to limit the call site, as in cases where we
might say "Only use this if it's attributable to an extension, etc).

 
   // Log memory statistics for the running processes, then discards a tab.
   // Tab discard happens sometime later, as collecting the statistics touches
   // multiple threads and takes time.
   void LogMemoryAndDiscardTab();
 
   // Log memory statistics for the running processes, then call the callback.
   void LogMemory(const std::string& title, const base::Closure& callback);
 
   // Used to set the test TickClock, which then gets used by NowTicks(). See
@@ skipping 18 matching lines @@
   // methods (about:discards for instance).
   bool IsTabAutoDiscardable(content::WebContents* contents) const;
 
   // Sets/clears the auto-discardable state of the tab.
   void SetTabAutoDiscardableState(content::WebContents* contents, bool state);
 
   // Returns true if |first| is considered less desirable to be killed than
   // |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);
   FRIEND_TEST_ALL_PREFIXES(TabManagerTest, ChildProcessNotifications);
   FRIEND_TEST_ALL_PREFIXES(TabManagerTest, Comparator);
   FRIEND_TEST_ALL_PREFIXES(TabManagerTest, DiscardedTabKeepsLastActiveTime);
   FRIEND_TEST_ALL_PREFIXES(TabManagerTest, DiscardWebContentsAt);
   FRIEND_TEST_ALL_PREFIXES(TabManagerTest, InvalidOrEmptyURL);
   FRIEND_TEST_ALL_PREFIXES(TabManagerTest, IsInternalPage);
   FRIEND_TEST_ALL_PREFIXES(TabManagerTest, OomPressureListener);
@@ skipping 210 matching lines @@
 
   // Weak pointer factory used for posting delayed tasks to task_runner_.
   base::WeakPtrFactory<TabManager> weak_ptr_factory_;
 
   DISALLOW_COPY_AND_ASSIGN(TabManager);
 };
 
 }  // namespace memory
 
 #endif  // CHROME_BROWSER_MEMORY_TAB_MANAGER_H_