memory metrics: record growth after purging BG renderer's cache

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 2f00381ad91e611ca56d9a88483b1f4e485134ba..9e8056e39b182a84939d73d0fb4fd3c4a82be0cb 100644
--- a/content/renderer/render_thread_impl.h
+++ b/content/renderer/render_thread_impl.h
@@ -562,7 +562,8 @@ class CONTENT_EXPORT RenderThreadImpl
   void OnRendererHidden();
   void OnRendererVisible();
 
-  void RecordPurgeAndSuspendMetrics() const;
+  void RecordPurgeAndSuspendMetrics();
+  void RecordPurgeAndSuspendMemoryGrowthMetrics() const;
 
   void ReleaseFreeMemory();
 
@@ -761,6 +762,8 @@ class CONTENT_EXPORT RenderThreadImpl
       thread_safe_render_message_filter_;
 
   base::CancelableClosure record_purge_suspend_metric_closure_;
+  RendererMemoryMetrics purge_and_suspend_memory_metrics_;
+  base::CancelableClosure record_purge_suspend_growth_metric_closure_;
 
   int32_t client_id_;