Add a histogram for renderer memory usage.

content/renderer/renderer_main.cc

Index: content/renderer/renderer_main.cc
diff --git a/content/renderer/renderer_main.cc b/content/renderer/renderer_main.cc
index 245064821a240e55dfd63bf4874e1e19d5a2d537..b3bae15339f8010c6aa40c07388319a80115c861 100644
--- a/content/renderer/renderer_main.cc
+++ b/content/renderer/renderer_main.cc
@@ -29,6 +29,7 @@
 #include "content/renderer/render_process_impl.h"
 #include "content/renderer/render_thread_impl.h"
 #include "content/renderer/renderer_main_platform_delegate.h"
+#include "third_party/WebKit/Source/Platform/chromium/public/Platform.h"
 #include "ui/base/ui_base_switches.h"
 #include "webkit/plugins/ppapi/ppapi_interface_factory.h"
 
@@ -43,6 +44,8 @@
 #include "third_party/WebKit/Source/WebKit/chromium/public/WebView.h"
 #endif  // OS_MACOSX
 
+using WebKit::Platform;
+
 namespace content {
 
 namespace {
@@ -109,13 +112,18 @@ class RendererMessageLoopObserver : public MessageLoop::TaskObserver {
             1, 3600000, 50, base::Histogram::kUmaTargetedHistogramFlag)) {}
   virtual ~RendererMessageLoopObserver() {}
 
-  virtual void WillProcessTask(base::TimeTicks time_posted) {
+  virtual void WillProcessTask(base::TimeTicks time_posted) OVERRIDE {
     begin_process_message_ = base::TimeTicks::Now();
   }
 
-  virtual void DidProcessTask(base::TimeTicks time_posted) {
+  virtual void DidProcessTask(base::TimeTicks time_posted) OVERRIDE {
     if (!begin_process_message_.is_null())
       process_times_->AddTime(base::TimeTicks::Now() - begin_process_message_);
+    if (Platform::current()) {
+      RenderThreadImpl* render_thread = RenderThreadImpl::current();
+      render_thread->histogram_customizer()->memory_renderer_used()->Add(
+          Platform::current()->memoryUsageMB() * 1024);
+    }
   }
 
  private: