benchmark.mojo: add time_between measurement type.

apps/benchmark/measurements.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 APPS_BENCHMARK_MEASUREMENTS_HH_
 #define APPS_BENCHMARK_MEASUREMENTS_HH_
 
 #include <vector>
 
 #include "apps/benchmark/event.h"
 #include "base/macros.h"
 #include "base/memory/scoped_ptr.h"
 #include "base/time/time.h"
 #include "base/values.h"
 
 namespace benchmark {
 
 // Describes a trace event to match.
 struct EventSpec {
   std::string name;
   std::string categories;
 
   EventSpec();
   EventSpec(std::string name, std::string categories);
   ~EventSpec();
 };
 
-enum class MeasurementType { TIME_UNTIL, AVG_DURATION };
+enum class MeasurementType { TIME_UNTIL, TIME_BETWEEN, AVG_DURATION };
 
 // Represents a single measurement to be performed on the collected trace.
 struct Measurement {
   MeasurementType type;
   EventSpec target_event;
+  // Second event targeted by the measurement, meaningful only for binary
+  // measurement types (TIME_BETWEEN).
+  EventSpec second_event;
   // Optional string from which this measurement was parsed. Can be used for
   // presentation purposes.
   std::string spec;
 
   Measurement();
+  Measurement(MeasurementType type, EventSpec target_event);
   Measurement(MeasurementType type,
-              std::string target_name,
-              std::string target_categories);
+              EventSpec target_event,
+              EventSpec second_event);
   ~Measurement();
 };
 
 class Measurements {
  public:
   Measurements(std::vector<Event> events, base::TimeTicks time_origin);
   ~Measurements();
 
   // Performs the given measurement. Returns the result in milliseconds or -1.0
   // if the measurement failed, e.g. because no events were matched.
   double Measure(const Measurement& measurement);
 
  private:
+  bool EarliestOccurence(const EventSpec& event_spec,
+                         base::TimeTicks* earliest);
   double TimeUntil(const EventSpec& event_spec);
+  double TimeBetween(const EventSpec& first_event_spec,
+                     const EventSpec& second_event_spec);
   double AvgDuration(const EventSpec& event_spec);
 
   std::vector<Event> events_;
   base::TimeTicks time_origin_;
   DISALLOW_COPY_AND_ASSIGN(Measurements);
 };
 
 }  // namespace benchmark
 
 #endif  // APPS_BENCHMARK_MEASUREMENTS_HH_