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

content/renderer/render_thread_impl.h

Index: content/renderer/render_thread_impl.h
diff --git a/content/renderer/render_thread_impl.h b/content/renderer/render_thread_impl.h
index cb03a378ca551c6f46100a6153101763938ac77a..cd1e2651b25bbeed19947e79bdf511e01f1e78b9 100644
--- a/content/renderer/render_thread_impl.h
+++ b/content/renderer/render_thread_impl.h
@@ -21,6 +21,7 @@
 #include "base/strings/string16.h"
 #include "base/threading/thread_checker.h"
 #include "base/timer/timer.h"
+#include "base/trace_event/malloc_dump_provider.h"
 #include "build/build_config.h"
 #include "content/child/child_thread_impl.h"
 #include "content/child/memory/child_memory_coordinator_impl.h"
@@ -38,6 +39,7 @@
 #include "net/base/network_change_notifier.h"
 #include "third_party/WebKit/public/platform/WebConnectionType.h"
 #include "third_party/WebKit/public/platform/scheduler/renderer/renderer_scheduler.h"
+#include "third_party/WebKit/public/web/WebMemoryStatistics.h"
 #include "ui/gfx/native_widget_types.h"
 
 #if defined(OS_MACOSX)
@@ -474,6 +476,12 @@ class CONTENT_EXPORT RenderThreadImpl
   bool OnControlMessageReceived(const IPC::Message& msg) override;
   void OnProcessBackgrounded(bool backgrounded) override;
   void OnProcessPurgeAndSuspend() override;
+  void OnDumpMemoryUsage();
+
+  blink::WebMemoryStatistics blink_memory_stats_;
+  base::trace_event::MallocStatistics malloc_stats_;
+  size_t discardable_stats_;
+
   void RecordAction(const base::UserMetricsAction& action) override;
   void RecordComputedAction(const std::string& action) override;