PerformanceMonitor: Add a new UMA histograms to track average CPU utilization

base/process/process_metrics.cc

 // Copyright 2013 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "base/process/process_metrics.h"
 
 #include "base/values.h"
 
 namespace base {
 
@@ skipping 24 matching lines @@
   res->Set("meminfo", memory_info_.ToValue().release());
   res->Set("diskinfo", disk_info_.ToValue().release());
 #endif
 #if defined(OS_CHROMEOS)
   res->Set("swapinfo", swap_info_.ToValue().release());
 #endif
 
   return res.PassAs<Value>();
 }
 
+double ProcessMetrics::GetPlatformIndependentCPUUsage() {
+#if defined(OS_WIN)
+  return GetCPUUsage() * processor_count_;
+#else
+  return GetCPUUsage();
+#endif
+}
+
 }  // namespace base