Add systemInfo.cpu.onUpdated event implementation.

chrome/browser/extensions/api/system_info_cpu/cpu_info_provider.h

 // Copyright (c) 2012 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_EXTENSIONS_API_SYSTEM_INFO_CPU_CPU_INFO_PROVIDER_H_
 #define CHROME_BROWSER_EXTENSIONS_API_SYSTEM_INFO_CPU_CPU_INFO_PROVIDER_H_
 
 #include "chrome/browser/extensions/system_info_provider.h"
 
 #include <vector>
 
+#include "base/timer.h"
 #include "chrome/common/extensions/api/experimental_system_info_cpu.h"
 
 namespace extensions {
 
 class CpuInfoProvider
     : public SystemInfoProvider<api::experimental_system_info_cpu::CpuInfo> {
  public:
-  typedef base::Callback<api::experimental_system_info_cpu::CpuUpdateInfo>
-      QueryCpuTimeCallback;
-  virtual ~CpuInfoProvider() {}
+  typedef base::Callback<
+      void(scoped_ptr<api::experimental_system_info_cpu::CpuUpdateInfo>)>
+          SamplingCallback;
+
+  virtual ~CpuInfoProvider();
 
   // Overriden from SystemInfoProvider<CpuInfo>.
   virtual bool QueryInfo(
       api::experimental_system_info_cpu::CpuInfo* info) OVERRIDE;
 
   // Start sampling the CPU usage. The callback gets called when one sampling
   // cycle is completed periodically with the CPU updated usage info for each
   // processors. Return true if it succeeds to start, otherwise, false is
-  // returned.
-  bool StartSampling(const QueryCpuTimeCallback& callback);
+  // returned. Can be called from any thread.

[Mihai Parparita -not on Chrome, 2012/09/16 06:23:05]

Allowing this to be called from any thread may mask bugs. Generally, all
extension function entry points are on the UI thread. It's better to check that
you're on the UI thread, and hand off execution to a StartSamplingOnFileThread
function (see
http://code.google.com/p/chromium/source/search?q=onfilethread+file%3Aextensions
for the pattern).

[Hongbo Min, 2012/09/16 14:07:49]

Done.

+  bool StartSampling(const SamplingCallback& callback);
 
-  // Stop the sampling cycle. Return true if it succeeds to stop.
+  // Stop the sampling cycle. Return true if it succeeds to stop. Can be called
+  // from any thread.
   bool StopSampling();
 
   // Return the single shared instance of CpuInfoProvider.
   static CpuInfoProvider* Get();
 
  private:
+  friend class SystemInfoProvider<api::experimental_system_info_cpu::CpuInfo>;
+  friend class MockCpuInfoProviderImpl;
+
   // The amount of time that CPU spent on performing different kinds of work.
   // It is used to calculate the usage percent for processors.
-  struct CpuTime {
+  class CpuTime {
+   public:
+    CpuTime() : user(0), kernel(0), idle(0) {}
     int64 user;   // user mode.
     int64 kernel; // kernel mode.
     int64 idle;   // twiddling thumbs.
   };
 
+  CpuInfoProvider();
+
   // Platform specific implementation for querying the CPU time information
   // for each processor. Note that the first element is the total aggregated
   // numbers of all logic processors.
-  bool QueryCpuTimePerProcessor(std::vector<CpuTime>* times);
+  virtual bool QueryCpuTimePerProcessor(std::vector<CpuTime>* times);
+
+  // Called when the sampling timer is expired.

[Mihai Parparita -not on Chrome, 2012/09/16 06:23:05]

"expired" doesn't seem right. "fired" perhaps?

[Hongbo Min, 2012/09/16 14:07:49]

Done.

+  void DoStartSampling();
+
+  // Indicates whether the CPU sampling is started.
+  bool is_sampling_started_;
+
+  // The sampling value returned from the most recent QueryCpuTimePerProcessor

[Mihai Parparita -not on Chrome, 2012/09/16 06:23:05]

This doesn't seem to be true. You set the variable when StartSampling is called,
but subsequent QueryCpuTimePerProcessor calls update a local variable only, and
compare that against the saved sampling_value_.  Call this start_cpu_time_ or
baseline_cpu_time_ instead?

[Hongbo Min, 2012/09/16 14:07:49]

Use baseline_cpu_time_. Done

+  // call.
+  std::vector<CpuTime> sampling_value_;
+
+  // The callback which will be called when one sampling cycle is completed.
+  SamplingCallback callback_;
+
+  // The timer used for polling CPU time periodically. Live on File thread.

[Mihai Parparita -not on Chrome, 2012/09/16 06:23:05]

"file thread" or "FILE thread" are the more common ways of capitalizing.

[Hongbo Min, 2012/09/16 14:07:49]

Done.

+  base::RepeatingTimer<CpuInfoProvider>* sampling_timer_;
+
+  // The time interval for sampling.

[Mihai Parparita -not on Chrome, 2012/09/16 06:23:05]

Mention the time units.

[Hongbo Min, 2012/09/16 14:07:49]

Done.

+  int sampling_interval_;
 };
 
 }  // namespace extensions
 
 #endif  // CHROME_BROWSER_EXTENSIONS_API_SYSTEM_INFO_CPU_CPU_INFO_PROVIDER_H_