Modify PurgeAndSuspend to see WebContents

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 582b2e667099f6fa0085f6721c4b9c69a37709c8..4901cd77ccdc41c88f46d6bb59b3c71c81cc49fd 100644
--- a/chrome/browser/memory/tab_manager.cc
+++ b/chrome/browser/memory/tab_manager.cc
@@ -670,6 +670,36 @@ void TabManager::UpdateTimerCallback() {
   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();
@@ -695,6 +725,8 @@ void TabManager::PurgeAndSuspendBackgroundedTabs() {
     // 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();
   }
 }