[Tentaive patch for discussion] Add Purge+Suspend metrics as UMA.

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..1daa6acd181f7a7756b7fd967fabdf041948d5d1 100644
--- a/chrome/browser/memory/tab_manager.cc
+++ b/chrome/browser/memory/tab_manager.cc
@@ -20,6 +20,7 @@
 #include "base/metrics/histogram_macros.h"
 #include "base/observer_list.h"
 #include "base/process/process.h"
+#include "base/process/process_metrics.h"
 #include "base/strings/string16.h"
 #include "base/strings/string_number_conversions.h"
 #include "base/strings/string_util.h"
@@ -670,6 +671,45 @@ 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")
+    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;
+
+  return true;
+}
+
+void TabManager::RecordPurgeAndSuspendMetrics(
+    const base::ProcessHandle& handle) {
+  std::unique_ptr<base::ProcessMetrics> process_metrics(
+      base::ProcessMetrics::CreateProcessMetrics(handle));
+  size_t private_bytes, shared_bytes;
+  if (process_metrics->GetMemoryBytes(&private_bytes, &shared_bytes)) {
+    UMA_HISTOGRAM_MEMORY_KB("Memory.PurgeAndSuspend.PrivateBytesKB",
+                            private_bytes);
+    UMA_HISTOGRAM_MEMORY_KB("Memory.PurgeAndSuspend.SharedBytesKB",
+                            shared_bytes);
+  }
+}
+
 void TabManager::PurgeAndSuspendBackgroundedTabs() {
   const base::CommandLine& command_line =
       *base::CommandLine::ForCurrentProcess();
@@ -695,7 +735,26 @@ void TabManager::PurgeAndSuspendBackgroundedTabs() {
     // timers if we want necessary and sufficient signals.
     if (tab.last_active > purge_and_suspend_time_threshold)
       continue;
-    tab.render_process_host->PurgeAndSuspend();
+
+    if (CanPurgeAndSuspendBackgroundedTab(tab.tab_contents_id))
+      continue;
+
+    if (tab.render_process_host->GetLastPurgeAndSuspendTime() <
+        tab.last_active) {
+      // If purge_and_suspend is disabled, PurgeAndSuspend() just updates
+      // LastPurgeAndSuspendTime. So we can avoid invoking
+      // RecordPurgeAndSuspendMetrics twice.
+      tab.render_process_host->PurgeAndSuspend();
+
+      if (!task_runner_.get())
+        task_runner_ = base::ThreadTaskRunnerHandle::Get();
+      task_runner_->PostDelayedTask(
+          FROM_HERE,
+          base::Bind(&TabManager::RecordPurgeAndSuspendMetrics,
+                     base::Unretained(this),
+                     base::ConstRef(tab.render_process_host->GetHandle())),
+          base::TimeDelta::FromSeconds(15));
+    }
   }
 }