Add guards to metric values; erase bad events/metrics from db

chrome/browser/performance_monitor/metric.cc

Index: chrome/browser/performance_monitor/metric.cc
diff --git a/chrome/browser/performance_monitor/metric.cc b/chrome/browser/performance_monitor/metric.cc
index 4d105f768c70d30b6e143b2bad73e2eb16a17f0c..2f28b0f0d39d4248112222ce570374491ac2ac41 100644
--- a/chrome/browser/performance_monitor/metric.cc
+++ b/chrome/browser/performance_monitor/metric.cc
@@ -4,21 +4,81 @@
 
 #include "chrome/browser/performance_monitor/metric.h"
 
+#include "base/basictypes.h"
 #include "base/logging.h"
 #include "base/string_number_conversions.h"
+#include "base/time.h"
+#include "chrome/browser/performance_monitor/constants.h"
 
 namespace performance_monitor {
 
+namespace {
+
+// For certain metrics (for instance, bytes read), it is possible that there is
+// no maximum value which we can safely assume.
+const double kNoMaximum = -1.0;
+
+// These constants are designed to keep metrics reasonable. However, due to the
+// variety of system configurations which can run chrome, these values may not
+// catch *all* erroneous values. For instance, on a one-CPU machine, any CPU
+// usage > 100 is erroneous, but on a 16-CPU machine, it's perfectly normal.
+// These are "best-guesses" in order to weed out obviously-false values. A
+// metric is valid if it is greater than or equal to the minimum and less than
+// the maximum, i.e. if it falls in the range [min, max).
+const double kMinUndefined = 0.0;
+const double kMaxUndefined = 0.0;  // No undefined metric is valid.
+const double kMinCpuUsage = 0.0;
+const double kMaxCpuUsage = 100000.0;  // 100% on a 1000-CPU machine.
+const double kMinPrivateMemoryUsage = 0.0;
+const double kMaxPrivateMemoryUsage = kBytesPerTerabyte;
+const double kMinSharedMemoryUsage = 0.0;
+const double kMaxSharedMemoryUsage = kBytesPerTerabyte;
+const double kMinStartupTime = 0.0;
+const double kMaxStartupTime = base::Time::kMicrosecondsPerMinute * 15.0;
+const double kMinTestStartupTime = 0.0;
+const double kMaxTestStartupTime = base::Time::kMicrosecondsPerMinute * 15.0;
+const double kMinSessionRestoreTime = 0.0;
+const double kMaxSessionRestoreTime = base::Time::kMicrosecondsPerMinute * 15.0;
+const double kMinPageLoadTime = 0.0;
+const double kMaxPageLoadTime = base::Time::kMicrosecondsPerMinute * 15.0;
+const double kMinNetworkBytesRead = 0.0;
+const double kMaxNetworkBytesRead = kNoMaximum;
+
+struct MetricBound {
+  double min;
+  double max;
+};
+
+const MetricBound kMetricBounds[] = {
+ { kMinUndefined, kMaxUndefined },
+ { kMinCpuUsage, kMaxCpuUsage },
+ { kMinPrivateMemoryUsage, kMaxPrivateMemoryUsage },
+ { kMinSharedMemoryUsage, kMaxSharedMemoryUsage },
+ { kMinStartupTime, kMaxStartupTime },
+ { kMinTestStartupTime, kMaxTestStartupTime },
+ { kMinSessionRestoreTime, kMaxSessionRestoreTime },
+ { kMinPageLoadTime, kMaxPageLoadTime },
+ { kMinNetworkBytesRead, kMaxNetworkBytesRead },
+};
+
+COMPILE_ASSERT(ARRAYSIZE_UNSAFE(kMetricBounds) == METRIC_NUMBER_OF_METRICS,
+               metric_bounds_size_doesnt_match_metric_count);
+
+}  // namespace
+
 Metric::Metric() {
   value = 0.0;
 }
 
-Metric::Metric(const base::Time& metric_time, const double metric_value)
-    : time(metric_time), value(metric_value) {
+Metric::Metric(MetricType metric_type,
+               const base::Time& metric_time,
+               const double metric_value)
+    : type(metric_type), time(metric_time), value(metric_value) {
 }
 
-Metric::Metric(const std::string& metric_time,
-               const std::string& metric_value) {
+Metric::Metric(MetricType metric_type,
+               const std::string& metric_time,
+               const std::string& metric_value) : type(metric_type) {
   int64 conversion = 0;
   base::StringToInt64(metric_time, &conversion);
   time = base::Time::FromInternalValue(conversion);
@@ -28,4 +88,15 @@ Metric::Metric(const std::string& metric_time,
 Metric::~Metric() {
 }
 
+bool Metric::IsValid() const {
+  return type < METRIC_NUMBER_OF_METRICS &&
+      (value < kMetricBounds[type].max ||
+          kMetricBounds[type].max == kNoMaximum) &&
+      value >= kMetricBounds[type].min;
+}
+
+std::string Metric::ValueAsString() const {
+  return base::DoubleToString(value);
+}
+
 }  // namespace performance_monitor