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

chrome/browser/memory/tab_manager_web_contents_data.cc

Index: chrome/browser/memory/tab_manager_web_contents_data.cc
diff --git a/chrome/browser/memory/tab_manager_web_contents_data.cc b/chrome/browser/memory/tab_manager_web_contents_data.cc
index 92ebc887cf0a8566ac907b3f32d449f356dc62d6..95786a29279bab5c7fbbe3476180d4e27edf51ac 100644
--- a/chrome/browser/memory/tab_manager_web_contents_data.cc
+++ b/chrome/browser/memory/tab_manager_web_contents_data.cc
@@ -22,9 +22,8 @@ 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_first_purge_(base::TimeDelta::FromMinutes(30)),
+      purge_state_(NOT_PURGED) {}
 
 TabManager::WebContentsData::~WebContentsData() {}
 
@@ -202,25 +201,21 @@ 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;
+void TabManager::WebContentsData::SetPurgeState(PurgeState state) {
+  purge_state_ = state;
 }
 
-base::TimeTicks TabManager::WebContentsData::LastPurgeAndSuspendModifiedTime()
-    const {
-  return last_purge_and_suspend_modified_time_;
+void TabManager::WebContentsData::SetTimeToFirstPurge(
+    const base::TimeDelta& time_to_first_purge) {
+  time_to_first_purge_ = time_to_first_purge;
 }
 
-void TabManager::WebContentsData::SetLastPurgeAndSuspendModifiedTimeForTesting(
-    base::TimeTicks timestamp) {
-  last_purge_and_suspend_modified_time_ = timestamp;
+base::TimeDelta TabManager::WebContentsData::TimeToFirstPurge() const {
+  return time_to_first_purge_;
 }
 
-TabManager::PurgeAndSuspendState
-TabManager::WebContentsData::GetPurgeAndSuspendState() const {
-  return purge_and_suspend_state_;
+TabManager::PurgeState TabManager::WebContentsData::GetPurgeState() const {
+  return purge_state_;
 }
 
 }  // namespace memory