Base: Add power requirements to the System monitor.

base/system_monitor/system_monitor.h

Index: base/system_monitor/system_monitor.h
===================================================================
--- base/system_monitor/system_monitor.h	(revision 137792)
+++ base/system_monitor/system_monitor.h	(working copy)
@@ -6,10 +6,13 @@
 #define BASE_SYSTEM_MONITOR_SYSTEM_MONITOR_H_
 #pragma once
 
+#include <map>
 #include <string>
+#include <utility>
 
 #include "base/base_export.h"
 #include "base/basictypes.h"
+#include "base/threading/thread_checker.h"
 #include "build/build_config.h"
 
 // Windows HiRes timers drain the battery faster so we need to know the battery
@@ -46,6 +49,13 @@
     RESUME_EVENT        // The system is being resumed.
   };
 
+  enum PowerRequirement {
+    DISPLAY_REQUIRED,   // The display should not be shut down.
+    SYSTEM_REQUIRED,    // The system should not be suspended.
+    CPU_REQUIRED,       // The process should not be suspended.
+    TEST_REQUIRED       // This is used by unit tests.
+  };
+
   typedef unsigned int DeviceIdType;
 
   // Create SystemMonitor. Only one SystemMonitor instance per application
@@ -145,6 +155,22 @@
                                   const FilePath& path);
   void ProcessMediaDeviceDetached(const DeviceIdType& id);
 
+  // Enters or leaves a period of time with a given |requirement|. If the
+  // operation has multiple requirements, make sure to use a unique |reason| for
+  // each one. Reusing the same |reason| is OK as far as the |requirement| is
+  // the same in every call, and each BeginPowerRequirement call is paired with
+  // a call to EndPowerRequirement. |reason| is expected to be an ASCII string.
+  // Must be called from the thread that created the SystemMonitor.
+  // Warning: Please remember that sleep deprivation is not a good thing; use
+  // with caution.
+  void BeginPowerRequirement(PowerRequirement requirement,
+                             const std::string& reason);
+  void EndPowerRequirement(PowerRequirement requirement,
+                           const std::string& reason);
+
+  // Returns the number of outsanding power requirement requests.
+  size_t GetPowerRequirementsCountForTest() const;
+
  private:
 #if defined(OS_MACOSX)
   void PlatformInit();
@@ -176,6 +202,11 @@
   bool battery_in_use_;
   bool suspended_;
 
+#if defined(OS_WIN)
+  std::map<std::string, std::pair<HANDLE, int> > handles_;
+  base::ThreadChecker thread_checker_;
+#endif
+
 #if defined(ENABLE_BATTERY_MONITORING)
   base::OneShotTimer<SystemMonitor> delayed_battery_check_;
 #endif