Revert of Add Resume logic of Purge+Suspend to TabManager.

chrome/browser/memory/tab_manager.cc

Index: chrome/browser/memory/tab_manager.cc
diff --git a/chrome/browser/memory/tab_manager.cc b/chrome/browser/memory/tab_manager.cc
index 339d7cd02a2a023ac6326b9f2ff6ec3f9ff318c7..b9c14301ffeb8115f0a4ea4682f81805efb4cee7 100644
--- a/chrome/browser/memory/tab_manager.cc
+++ b/chrome/browser/memory/tab_manager.cc
@@ -84,14 +84,6 @@
 // machine was suspended and correct the timing statistics.
 const int kSuspendThresholdSeconds = kAdjustmentIntervalSeconds * 4;
 
-// A suspended renderer is suspended for this duration.
-constexpr base::TimeDelta kDurationOfRendererSuspension =
-    base::TimeDelta::FromSeconds(120);
-
-// A resumed renderer is resumed for this duration.
-constexpr base::TimeDelta kDurationOfRendererResumption =
-    base::TimeDelta::FromSeconds(10);
-
 // The time during which a tab is protected from discarding after it stops being
 // audible.
 const int kAudioProtectionTimeSeconds = 60;
@@ -426,23 +418,17 @@
   GetWebContentsData(contents)->SetAutoDiscardableState(state);
 }
 
-content::WebContents* TabManager::GetWebContentsById(int64_t tab_contents_id) {
-  TabStripModel* model = nullptr;
-  int index = FindTabStripModelById(tab_contents_id, &model);
-  if (index == -1)
-    return nullptr;
-  return model->GetWebContentsAt(index);
-}
-
 bool TabManager::CanSuspendBackgroundedRenderer(int render_process_id) {
   // A renderer can be suspended if it's not playing media.
   auto tab_stats = GetUnsortedTabStats();
   for (auto& tab : tab_stats) {
     if (tab.child_process_host_id != render_process_id)
       continue;
-    WebContents* web_contents = GetWebContentsById(tab.tab_contents_id);
-    if (!web_contents)
+    TabStripModel* model;
+    int index = FindTabStripModelById(tab.tab_contents_id, &model);
+    if (index == -1)
       return false;
+    WebContents* web_contents = model->GetWebContentsAt(index);
     if (IsMediaTab(web_contents))
       return false;
   }
@@ -701,33 +687,6 @@
   PurgeAndSuspendBackgroundedTabs();
 }
 
-TabManager::PurgeAndSuspendState TabManager::GetNextPurgeAndSuspendState(
-    content::WebContents* content,
-    base::TimeTicks current_time,
-    const base::TimeDelta& time_to_first_suspension) const {
-  DCHECK(content);
-  PurgeAndSuspendState state =
-      GetWebContentsData(content)->GetPurgeAndSuspendState();
-
-  auto time_passed = current_time -
-      GetWebContentsData(content)->LastPurgeAndSuspendModifiedTime();
-  switch (state) {
-    case RUNNING:
-      if (time_passed > time_to_first_suspension)
-        return SUSPENDED;
-      break;
-    case RESUMED:
-      if (time_passed > kDurationOfRendererResumption)
-        return SUSPENDED;
-      break;
-    case SUSPENDED:
-      if (time_passed > kDurationOfRendererSuspension)
-        return RESUMED;
-      break;
-  }
-  return state;
-}
-
 void TabManager::PurgeAndSuspendBackgroundedTabs() {
   const base::CommandLine& command_line =
       *base::CommandLine::ForCurrentProcess();
@@ -741,48 +700,21 @@
   }
   if (purge_and_suspend_time <= 0)
     return;
-  base::TimeTicks current_time = NowTicks();
-  base::TimeDelta time_to_first_suspension =
-      base::TimeDelta::FromSeconds(purge_and_suspend_time);
+  auto purge_and_suspend_time_threshold =
+      NowTicks() - base::TimeDelta::FromSeconds(purge_and_suspend_time);
   auto tab_stats = GetUnsortedTabStats();
   for (auto& tab : tab_stats) {
     if (!tab.render_process_host->IsProcessBackgrounded())
       continue;
-    if (!CanSuspendBackgroundedRenderer(tab.child_process_host_id))
-      continue;
-
-    WebContents* content = GetWebContentsById(tab.tab_contents_id);
-    if (!content)
-      continue;
-
-    PurgeAndSuspendState current_state =
-        GetWebContentsData(content)->GetPurgeAndSuspendState();
-    // If the tab's purge-and-suspend state is not RUNNING, the tab should be
-    // backgrounded. Since tab.last_hidden is updated everytime the tab is
-    // hidden, we should see tab.last_hidden < last_modified_time.
-    DCHECK(current_state == RUNNING ||
-           tab.last_hidden <
-               GetWebContentsData(content)->LastPurgeAndSuspendModifiedTime());
-    PurgeAndSuspendState next_state = GetNextPurgeAndSuspendState(
-        content, current_time, time_to_first_suspension);
-    if (current_state == next_state)
-      continue;
-
     // TODO(hajimehoshi): Now calling PurgeAndSuspend is implemented without
     // timers for simplicity, so PurgeAndSuspend is called even after the
     // renderer is purged and suspended once. This should be replaced with
     // timers if we want necessary and sufficient signals.
-    GetWebContentsData(content)->SetPurgeAndSuspendState(next_state);
-    switch (next_state) {
-      case SUSPENDED:
-        tab.render_process_host->PurgeAndSuspend();
-        break;
-      case RESUMED:
-        tab.render_process_host->Resume();
-        break;
-      case RUNNING:
-        NOTREACHED();
-    }
+    if (tab.last_hidden > purge_and_suspend_time_threshold)
+      continue;
+    if (!CanSuspendBackgroundedRenderer(tab.child_process_host_id))
+      continue;
+    tab.render_process_host->PurgeAndSuspend();
   }
 }
 
@@ -883,7 +815,6 @@
                                   int index,
                                   int reason) {
   GetWebContentsData(new_contents)->SetDiscardState(false);
-  GetWebContentsData(new_contents)->SetPurgeAndSuspendState(RUNNING);
   // If |old_contents| is set, that tab has switched from being active to
   // inactive, so record the time of that transition.
   if (old_contents)