Remove the unmaintained performance monitor.

chrome/browser/performance_monitor/process_metrics_history.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 <limits>
 
 #include "base/logging.h"
 #include "base/metrics/histogram.h"
 #include "base/process/process_metrics.h"
 
-#include "chrome/browser/performance_monitor/constants.h"
 #include "chrome/browser/performance_monitor/process_metrics_history.h"
 #if defined(OS_MACOSX)
 #include "content/public/browser/browser_child_process_host.h"
 #endif
 #include "content/public/common/process_type.h"
 
 namespace performance_monitor {
 
+// If a process is consistently above this CPU utilization percentage over time,
+// we consider it as high and may take action.
+const float kHighCPUUtilizationThreshold = 90.0f;
+
 ProcessMetricsHistory::ProcessMetricsHistory()
     : process_handle_(0),
       process_type_(content::PROCESS_TYPE_UNKNOWN),
       last_update_sequence_(0) {
   ResetCounters();
 }
 
 ProcessMetricsHistory::~ProcessMetricsHistory() {}
 
 void ProcessMetricsHistory::ResetCounters() {
@@ skipping 97 matching lines @@
           kHistogramMin, kHistogramMax, kHistogramBucketCount);
       if (min_cpu_usage_ > kHighCPUUtilizationThreshold)
         UMA_HISTOGRAM_BOOLEAN("PerformanceMonitor.HighCPU.PPAPIProcess", true);
       break;
     default:
       break;
   }
 }
 
 }  // namespace performance_monitor