Add peak memory usage metric

chrome/browser/metrics/metrics_memory_details.h

 // Copyright 2015 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.
 
 #ifndef CHROME_BROWSER_METRICS_METRICS_MEMORY_DETAILS_H_
 #define CHROME_BROWSER_METRICS_METRICS_MEMORY_DETAILS_H_
 
 #include <map>
 
 #include "base/callback.h"
@@ skipping 20 matching lines @@
 
  private:
   // Latest metrics about record time and memory usage at that time per process.
   // The second values of |memory_sizes_| are in kB.
   std::map<base::ProcessId, base::TimeTicks> times_;
   std::map<base::ProcessId, int> memory_sizes_;
 
   DISALLOW_COPY_AND_ASSIGN(MemoryGrowthTracker);
 };
 
+// PeakMemoryUsageTracker tracks the peak memory usage.
+class PeakMemoryUsageTracker {
+ public:
+  PeakMemoryUsageTracker();
+
+  // Call with current memory usage. Returns true if the peak has been updated.
+  bool Update(int memory_usage);

[haraken, 2016/12/12 11:41:00]

unsigned long long?

+  int peak() { return peak_; }
+
+ private:
+  int peak_;

[haraken, 2016/12/12 11:41:00]

unsigned long long?

+
+  DISALLOW_COPY_AND_ASSIGN(PeakMemoryUsageTracker);
+};
+
 // Handles asynchronous fetching of memory details and logging histograms about
 // memory use of various processes.
 // Will run the provided callback when finished.
 class MetricsMemoryDetails : public MemoryDetails {
  public:
   MetricsMemoryDetails(const base::Closure& callback,
-                       MemoryGrowthTracker* memory_growth_tracker);
+                       MemoryGrowthTracker* memory_growth_tracker,
+                       PeakMemoryUsageTracker* peak_memory_usage_tracker);
 
   void set_generate_histograms(bool generate_histograms) {
     generate_histograms_ = generate_histograms;
   }
 
  protected:
   ~MetricsMemoryDetails() override;
 
   // MemoryDetails:
   void OnDetailsAvailable() override;
@@ skipping 10 matching lines @@
   // Update histograms on memory growth or shrink in renderer processes.
   void AnalyzeMemoryGrowth();
 
   base::Closure callback_;
 
   // A pointer to MemoryGrowthTracker which is contained in a longer-lived
   // owner of MetricsMemoryDetails, for example, ChromeMetricsServiceClient.
   // If it is null, nothing is tracked.
   MemoryGrowthTracker* memory_growth_tracker_;
 
+  // A pointer to PeakMemoryUsageTracker which is contained in a longer-lived
+  // owner of MetricsMemoryDetails, for example, ChromeMetricsServiceClient.
+  // If it is null, nothing is tracked.
+  PeakMemoryUsageTracker* peak_memory_usage_tracker_;
+
   // A flag indicating if histogram data should be generated. True on default.
   // If false, then only MemoryGrowthTracker gets notified about memory usage.
   bool generate_histograms_;
 
   DISALLOW_COPY_AND_ASSIGN(MetricsMemoryDetails);
 };
 
 #endif  // CHROME_BROWSER_METRICS_METRICS_MEMORY_DETAILS_H_