Experimental 'purging and suspending' backgrounded tabs behind the flag

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 de82f58f8eaf193469a31e878cd0bef17af5b9ee..501d6d2d2bf349a918898c14ce3e49d329e52a21 100644
--- a/chrome/browser/memory/tab_manager.cc
+++ b/chrome/browser/memory/tab_manager.cc
@@ -41,6 +41,7 @@
 #include "chrome/browser/ui/tabs/tab_utils.h"
 #include "chrome/common/chrome_constants.h"
 #include "chrome/common/chrome_features.h"
+#include "chrome/common/chrome_switches.h"
 #include "chrome/common/url_constants.h"
 #include "components/metrics/system_memory_stats_recorder.h"
 #include "components/variations/variations_associated_data.h"
@@ -484,7 +485,7 @@ void TabManager::AddTabStats(const TabStripModel* model,
                              bool is_app,
                              bool active_model,
                              TabStatsList* stats_list) {
-for (int i = 0; i < model->count(); i++) {
+  for (int i = 0; i < model->count(); i++) {
     WebContents* contents = model->GetWebContentsAt(i);
     if (!contents->IsCrashed()) {
       TabStats stats;
@@ -541,6 +542,36 @@ void TabManager::UpdateTimerCallback() {
   // This starts the CrOS specific OOM adjustments in /proc/<pid>/oom_score_adj.
   delegate_->AdjustOomPriorities(stats_list);
 #endif
+
+  PurgeAndSuspendBackgroundedTabs();
+}
+
+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_delta = 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.
+    if (NowTicks() - tab.last_active < purge_and_suspend_time_delta)

[dcheng, 2016/05/10 04:49:53]

Nit: maybe just get NowTicks() once outside the loop and then just do a simple
comparison in here? e.g.

auto purge_and_suspend_threshhold  = NowTicks() -
base::TimeDelta::FromSeconds(purge_and_suspend_time);

for (...) {
  if (tab.last_active < purge_and_suspend_threshhold)
  /* ... */
}

[hajimehoshi, 2016/05/10 06:54:11]

Done.

+      continue;
+    tab.render_process_host->PurgeAndSuspend();
+  }
 }
 
 bool TabManager::CanDiscardTab(int64_t target_web_contents_id) const {