[TabManager] Protect tabs opened in background.

chrome/browser/memory/tab_manager.cc

 // 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.
 
 #include "chrome/browser/memory/tab_manager.h"
 
 #include <stddef.h>
 
 #include <algorithm>
 #include <set>
@@ skipping 343 matching lines @@
                                   content::WebContents* new_contents,
                                   int index,
                                   int reason) {
   GetWebContentsData(new_contents)->SetDiscardState(false);
   // If |old_contents| is set, that tab has switched from being active to
   // inactive, so record the time of that transition.
   if (old_contents)
     GetWebContentsData(old_contents)->SetLastInactiveTime(NowTicks());
 }
 
+void TabManager::TabInsertedAt(content::WebContents* contents,
+                               int index,
+                               bool foreground) {
+  // Only interested in background tabs, as foreground tabs get taken care of by
+  // ActiveTabChanged.
+  if (foreground)
+    return;
+
+  // A new background tab is similar to having a tab switch from being active to
+  // inactive.
+  GetWebContentsData(contents)->SetLastInactiveTime(NowTicks());
+}
+
 ///////////////////////////////////////////////////////////////////////////////
 // TabManager, private:
 
 // static
 void TabManager::PurgeMemoryAndDiscardTab() {
   if (g_browser_process && g_browser_process->GetTabManager()) {
     TabManager* manager = g_browser_process->GetTabManager();
     manager->PurgeBrowserMemory();
     manager->DiscardTab();
   }
@@ skipping 426 matching lines @@
   // Schedule another notification. Use a weak pointer so this doesn't explode
   // during tear down.
   task_runner_->PostDelayedTask(
       FROM_HERE,
       base::Bind(&TabManager::DoChildProcessDispatch,
                  weak_ptr_factory_.GetWeakPtr()),
       base::TimeDelta::FromSeconds(kRendererNotificationDelayInSeconds));
 }
 
 }  // namespace memory