Add peak memory usage metric

chrome/browser/metrics/metrics_memory_details.cc

Index: chrome/browser/metrics/metrics_memory_details.cc
diff --git a/chrome/browser/metrics/metrics_memory_details.cc b/chrome/browser/metrics/metrics_memory_details.cc
index 807bc0921b82f41e578cee406727cbf81181799d..316d1a6f606aedbb2ab6e4ce8427634eeff317fb 100644
--- a/chrome/browser/metrics/metrics_memory_details.cc
+++ b/chrome/browser/metrics/metrics_memory_details.cc
@@ -12,6 +12,7 @@
 #include "base/metrics/histogram_macros.h"
 #include "base/single_thread_task_runner.h"
 #include "base/strings/utf_string_conversions.h"
+#include "base/sys_info.h"
 #include "base/threading/thread_task_runner_handle.h"
 #include "build/build_config.h"
 #include "components/nacl/common/nacl_process_type.h"
@@ -56,11 +57,23 @@ bool MemoryGrowthTracker::UpdateSample(base::ProcessId pid,
   return false;
 }
 
+PeakMemoryUsageTracker::PeakMemoryUsageTracker() : peak_(0) {}
+
+bool PeakMemoryUsageTracker::Update(int memory_usage) {
+  if (memory_usage > peak_) {
+    peak_ = memory_usage;
+    return true;
+  }
+  return false;
+}
+
 MetricsMemoryDetails::MetricsMemoryDetails(
     const base::Closure& callback,
-    MemoryGrowthTracker* memory_growth_tracker)
+    MemoryGrowthTracker* memory_growth_tracker,
+    PeakMemoryUsageTracker* peak_memory_usage_tracker)
     : callback_(callback),
       memory_growth_tracker_(memory_growth_tracker),
+      peak_memory_usage_tracker_(peak_memory_usage_tracker),
       generate_histograms_(true) {}
 
 MetricsMemoryDetails::~MetricsMemoryDetails() {
@@ -199,6 +212,25 @@ void MetricsMemoryDetails::UpdateHistograms() {
   int total_sample = static_cast<int>(aggregate_memory / 1024);
   UMA_HISTOGRAM_MEMORY_LARGE_MB("Memory.Total2", total_sample);
 
+  if (peak_memory_usage_tracker_) {
+    int previous_peak = peak_memory_usage_tracker_->peak();
+    if (peak_memory_usage_tracker_->Update(
+            static_cast<int>(aggregate_memory))) {
+      int physical_memory =
+          static_cast<int>(base::SysInfo::AmountOfPhysicalMemory());
+      int previous_peak_percentage = std::min(
+          static_cast<int>(100.0 * previous_peak / physical_memory), 100);
+      int new_peak_percentage =
+          std::min(static_cast<int>(100.0 * peak_memory_usage_tracker_->peak() /
+                                    physical_memory),
+                   100);
+      for (int i = previous_peak_percentage + 1; i <= new_peak_percentage;
+           ++i) {
+        UMA_HISTOGRAM_COUNTS_100("Memory.Total2.RelativePeak", i);
+      }
+    }
+  }
+
   // Predict the number of processes needed when isolating all sites and when
   // isolating only HTTPS sites.
   int all_renderer_count = renderer_count + chrome_count + extension_count;