WebUI TaskManager: Add "Activate page" feature.

chrome/browser/task_manager/task_manager.cc

 // Copyright (c) 2011 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/task_manager/task_manager.h"
 
 #include "base/compiler_specific.h"
 #include "base/i18n/number_formatting.h"
 #include "base/i18n/rtl.h"
 #include "base/process_util.h"
@@ skipping 548 matching lines @@
 
 bool TaskManagerModel::GetV8Memory(int index, size_t* result) const {
   *result = 0;
   if (!resources_[index]->ReportsV8MemoryStats())
     return false;
 
   *result = resources_[index]->GetV8MemoryAllocated();
   return true;
 }
 
+bool TaskManagerModel::CanActivate(int index) const {
+  CHECK_LT(index, ResourceCount());
+  return GetResourceTabContents(index) != NULL;
+}
+
 bool TaskManagerModel::CanInspect(int index) const {
   CHECK_LT(index, ResourceCount());
   return resources_[index]->CanInspect();
 }
 
 void TaskManagerModel::Inspect(int index) const {
   CHECK_LT(index, ResourceCount());
   resources_[index]->Inspect();
 }
 
@@ skipping 557 matching lines @@
     // Count the number of extensions with background pages (including
     // incognito).
     count += CountExtensionBackgroundPagesForProfile(profile);
     if (profile->HasOffTheRecordProfile()) {
       count += CountExtensionBackgroundPagesForProfile(
           profile->GetOffTheRecordProfile());
     }
   }
   return count;
 }