Modify PurgeAndSuspend to see WebContents

chrome/browser/memory/tab_manager.cc

 // Copyright (c) 2012 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.h"
 
 #include <stddef.h>
 
 #include <algorithm>
 #include <set>
@@ skipping 652 matching lines @@
 
 #if defined(OS_CHROMEOS)
   TabStatsList stats_list = GetTabStats();
   // This starts the CrOS specific OOM adjustments in /proc/<pid>/oom_score_adj.
   delegate_->AdjustOomPriorities(stats_list);
 #endif
 
   PurgeAndSuspendBackgroundedTabs();
 }
 
+bool TabManager::CanPurgeAndSuspendBackgroundedTab(
+    int64_t target_web_contents_id) const {
+  TabStripModel* model;
+  int idx = FindTabStripModelById(target_web_contents_id, &model);
+  if (idx == -1)
+    return false;
+
+  WebContents* web_contents = model->GetWebContentsAt(idx);
+
+  // Do not suspend tabs that are playing either playing audio or accessing the
+  // microphone or camera as it's too distruptive to the user experience.
+  if (IsMediaTab(web_contents))

[chrisha, 2016/10/04 21:52:41]

This is the only reason I think we shouldn't suspend: the tab is effectively a
foreground tab (visible, or playing audio).

[tasak, 2016/10/05 05:28:46]

I see.
Done.

+    return false;
+
+  // Do not discard a recently used tab.

[Georges Khalil, 2016/10/04 13:28:55]

nit: s/discard/suspend.

[chrisha, 2016/10/04 21:52:41]

I don't think this is necessary. We should feel free to suspend recently used
tabs, as the cost of unsuspending them is effectively nothing (as shown in early
testing).

[tasak, 2016/10/05 05:28:46]

Done.

+  if (minimum_protection_time_.InSeconds() > 0) {
+    auto delta =
+        NowTicks() - GetWebContentsData(web_contents)->LastInactiveTime();
+    if (delta < minimum_protection_time_)
+      return false;

[Georges Khalil, 2016/10/04 13:28:55]

nit: Let's move this logic to a function, instead of duplicating it. Something
like "IsTabTimeProtected".

+  }
+
+  // Do not purge and suspend a tab that was explicitly disallowed to.
+  // Note: reused tab discarding logic.
+  if (!IsTabAutoDiscardable(web_contents))

[chrisha, 2016/10/04 21:52:41]

Discarding logic shouldn't affect suspending, IMO.

[tasak, 2016/10/05 05:28:46]

I see.
If needed, I will update src/chrome/common/extensions/api/tabs.json.

+    return false;
+
+  return true;
+}
+
 void TabManager::PurgeAndSuspendBackgroundedTabs() {
   const base::CommandLine& command_line =
       *base::CommandLine::ForCurrentProcess();
   if (!command_line.HasSwitch(switches::kPurgeAndSuspendTime))
     return;
   int purge_and_suspend_time = 0;
   if (!base::StringToInt(
           command_line.GetSwitchValueASCII(switches::kPurgeAndSuspendTime),
           &purge_and_suspend_time)) {
     return;
   }
   if (purge_and_suspend_time <= 0)
     return;
   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;
     // 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.
     if (tab.last_active > purge_and_suspend_time_threshold)
       continue;
+    if (!CanPurgeAndSuspendBackgroundedTab(tab.tab_contents_id))
+      continue;
     tab.render_process_host->PurgeAndSuspend();
   }
 }
 
 WebContents* TabManager::DiscardWebContentsAt(int index, TabStripModel* model) {
   // Can't discard active index.
   if (model->active_index() == index)
     return nullptr;
 
   WebContents* old_contents = model->GetWebContentsAt(index);
@@ skipping 232 matching lines @@
   // platform.
   std::string allow_multiple_discards = variations::GetVariationParamValue(
       features::kAutomaticTabDiscarding.name, "AllowMultipleDiscards");
   return (allow_multiple_discards != "true");
 #else
   return false;
 #endif
 }
 
 }  // namespace memory