PerformanceMonitor: UMA alert for high browser CPU usage.

chrome/browser/performance_monitor/constants.h

Index: chrome/browser/performance_monitor/constants.h
diff --git a/chrome/browser/performance_monitor/constants.h b/chrome/browser/performance_monitor/constants.h
index 168baf22194ef083cc18f1f29c521d7c8cdf2aee..84dfb8ea775f3463e3dae46e0127e50dd6e34733 100644
--- a/chrome/browser/performance_monitor/constants.h
+++ b/chrome/browser/performance_monitor/constants.h
@@ -21,6 +21,8 @@ extern const char kProcessChromeAggregate[];
 extern const char kStateChromeVersion[];
 extern const char kStateProfilePrefix[];
 
+// The interval the watched processes are sampled for performance metrics.
+const int kSampleIntervalInSeconds = 10;
 // The default interval at which PerformanceMonitor performs its timed
 // collections; this can be overridden by using the kPerformanceMonitorGathering
 // switch with an associated (positive integer) value.
@@ -41,6 +43,11 @@ const int64 kBytesPerTerabyte = kBytesPerGigabyte * (1 << 10);
 const int64 kMicrosecondsPerMonth = base::Time::kMicrosecondsPerDay * 30;
 const int64 kMicrosecondsPerYear = base::Time::kMicrosecondsPerDay * 365;
 
+// Performance alert thresholds
+
+// 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;
 }  // namespace performance_monitor
 
 #endif  // CHROME_BROWSER_PERFORMANCE_MONITOR_CONSTANTS_H_