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..e7a27b896fe08953bbe1c5a7df847445fa5d15c7 100644
--- a/chrome/browser/memory/tab_manager.cc
+++ b/chrome/browser/memory/tab_manager.cc
@@ -670,6 +670,31 @@ 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))
+    return false;
+
+  if (web_contents->GetContentsMimeType() == "application/pdf")

[haraken, 2016/10/03 06:32:35]

I don't think this check is needed. It will be safe to suspend application/pdf
tabs (although I'm not sure how much memory we can save by suspending them).

[tasak, 2016/10/03 07:08:54]

Done.

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

[haraken, 2016/10/03 06:32:35]

I'd add the minimum_protection_time_ check we have in TabManager::CanDiscardTab.

[tasak, 2016/10/03 07:08:54]

Done.

+  return true;
+}
+
 void TabManager::PurgeAndSuspendBackgroundedTabs() {
   const base::CommandLine& command_line =
       *base::CommandLine::ForCurrentProcess();
@@ -695,6 +720,8 @@ 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();
   }
 }