Resume a backgrounded renderer that was purged and suspended

chrome/browser/memory/tab_manager_web_contents_data.cc

 // Copyright 2015 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_web_contents_data.h"
 
 #include "base/metrics/histogram_macros.h"
 #include "base/time/tick_clock.h"
 #include "chrome/browser/browser_process.h"
 #include "chrome/browser/engagement/site_engagement_service.h"
 #include "chrome/browser/profiles/profile.h"
 #include "content/public/browser/browser_thread.h"
 #include "content/public/browser/web_contents.h"
 
 using base::TimeTicks;
 using content::WebContents;
 
 DEFINE_WEB_CONTENTS_USER_DATA_KEY(memory::TabManager::WebContentsData);
 
 namespace memory {
 
 TabManager::WebContentsData::WebContentsData(content::WebContents* web_contents)
-    : WebContentsObserver(web_contents), test_tick_clock_(nullptr) {}
+    : WebContentsObserver(web_contents),
+      test_tick_clock_(nullptr),
+      last_purge_and_suspend_modified_time_(
+          base::TimeTicks::FromInternalValue(0)),
+      purge_and_suspend_state_(BACKGROUNDED) {}

[haraken, 2016/10/19 08:57:54]

Is it okay to unconditionally set the initial value to BACKGROUNDED (even though
the WebContentsData is foregrounded)?

[tasak, 2016/10/19 10:17:13]

In PurgeAndSuspendBackgroundedTabs, firstly we check whether a tab is
backgrounded or not.
So we don't need to consider "foregrounded".

 
 TabManager::WebContentsData::~WebContentsData() {}
 
 void TabManager::WebContentsData::DidStartLoading() {
   // Marks the tab as no longer discarded if it has been reloaded from another
   // source (ie: context menu).
   SetDiscardState(false);
 }
 
 void TabManager::WebContentsData::WebContentsDestroyed() {
@@ skipping 157 matching lines @@
 
   tab_data_.is_auto_discardable = state;
   g_browser_process->GetTabManager()->OnAutoDiscardableStateChange(
       web_contents(), state);
 }
 
 bool TabManager::WebContentsData::IsAutoDiscardable() {
   return tab_data_.is_auto_discardable;
 }
 
+void TabManager::WebContentsData::SetPurgeAndSuspendState(
+    PurgeAndSuspendState state) {
+  last_purge_and_suspend_modified_time_ = TimeTicks::Now();
+  purge_and_suspend_state_ = state;
+}
+
+base::TimeTicks TabManager::WebContentsData::LastPurgeAndSuspendModifiedTime()
+    const {
+  return last_purge_and_suspend_modified_time_;
+}
+
+TabManager::PurgeAndSuspendState
+TabManager::WebContentsData::GetPurgeAndSuspendState() const {
+  return purge_and_suspend_state_;
+}
+
 }  // namespace memory