Purge once random minutes(between 30min and 60min) after backgrounded.

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),
-      last_purge_and_suspend_modified_time_(
-          base::TimeTicks::FromInternalValue(0)),
-      purge_and_suspend_state_(RUNNING) {}
+      time_to_purge_(base::TimeDelta::FromMinutes(30)),
+      is_purged_(false) {}
 
 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_ = NowTicks();
-  purge_and_suspend_state_ = state;
-}
-
-base::TimeTicks TabManager::WebContentsData::LastPurgeAndSuspendModifiedTime()
-    const {
-  return last_purge_and_suspend_modified_time_;
-}
-
-void TabManager::WebContentsData::SetLastPurgeAndSuspendModifiedTimeForTesting(
-    base::TimeTicks timestamp) {
-  last_purge_and_suspend_modified_time_ = timestamp;
-}
-
-TabManager::PurgeAndSuspendState
-TabManager::WebContentsData::GetPurgeAndSuspendState() const {
-  return purge_and_suspend_state_;
-}
-
 }  // namespace memory