Created multi-process-friendly PowerMonitor interface.

base/power_monitor/power_monitor.cc

Index: base/power_monitor/power_monitor.cc
diff --git a/base/power_monitor/power_monitor.cc b/base/power_monitor/power_monitor.cc
index 87188f1c591eb1c6a4bdf38bacc4125f045b91bd..7bb1f473a747fc7ed440ef1f0fbd32605d1ec005 100644
--- a/base/power_monitor/power_monitor.cc
+++ b/base/power_monitor/power_monitor.cc
@@ -4,40 +4,33 @@
 
 #include "base/power_monitor/power_monitor.h"
 
-#include "base/time/time.h"
+#include "base/power_monitor/power_monitor_device_source.h"
 
 namespace base {
 
 static PowerMonitor* g_power_monitor = NULL;
 
-#if defined(ENABLE_BATTERY_MONITORING)
-// The amount of time (in ms) to wait before running the initial
-// battery check.
-static int kDelayedBatteryCheckMs = 10 * 1000;
-#endif  // defined(ENABLE_BATTERY_MONITORING)
-
+// This constructor is provided to preserve backwards compatibility with the
+// most common use case, where the power monitor is created on a UI thread to
+// directly monitor system power events.
+//
+// TODO(bajones): Update all instances of PowerMonitor to pass in an explicit
+// new PowerMonitorDeviceSource()

[palmer, 2013/07/09 21:16:10]

Maybe this is the real fix, rather than DCHECKing on process type. (Then you
could just get rid of the 0-arg constructor.) How bad is it if anyone uses this
version of the constructor in a non-browser process?

[vandebo (ex-Chrome), 2013/07/09 22:22:08]

All that will happen if the 0-arg constructor is used in a non-browser process
is that it won't work.  Renderer processes already have this problem and (since
it was found and worked around) it hasn't caused any noticeable negative
affects.

[bajones, 2013/07/09 22:28:00]

If used on a non-browser process then they most likely won't get power events at
all.

I left this in place to avoid touching even more files in this already large CL,
but it's not unreasonable to update everything. The constructor would need to be
updated in:

src/base/power_monitor/power_monitor_unittest.cc
src/chrome/browser/extensions/event_router_forwarder_unittest.cc
src/chrome/nacl/nacl_main.cc
src/content/browser/browser_main_loop.cc
src/content/plugin/plugin_main.cc
src/content/renderer/renderer_main.cc // Shouldn't be here in the first place,
actually...
src/content/utility/utility_main.cc
src/content/worker/worker_main.cc	

 PowerMonitor::PowerMonitor()
     : observers_(new ObserverListThreadSafe<PowerObserver>()),
-      battery_in_use_(false),
-      suspended_(false) {
+      source_(new PowerMonitorDeviceSource()) {
   DCHECK(!g_power_monitor);
   g_power_monitor = this;
+}
 
-  DCHECK(MessageLoop::current());
-#if defined(ENABLE_BATTERY_MONITORING)
-  delayed_battery_check_.Start(FROM_HERE,
-      base::TimeDelta::FromMilliseconds(kDelayedBatteryCheckMs), this,
-      &PowerMonitor::BatteryCheck);
-#endif  // defined(ENABLE_BATTERY_MONITORING)
-#if defined(OS_MACOSX)
-  PlatformInit();
-#endif
+PowerMonitor::PowerMonitor(PowerMonitorSource* source)
+    : observers_(new ObserverListThreadSafe<PowerObserver>()),
+      source_(source) {
+  DCHECK(!g_power_monitor);
+  g_power_monitor = this;
 }
 
 PowerMonitor::~PowerMonitor() {
-#if defined(OS_MACOSX)
-  PlatformDestroy();
-#endif
   DCHECK_EQ(this, g_power_monitor);
   g_power_monitor = NULL;
 }
@@ -55,42 +48,18 @@ void PowerMonitor::RemoveObserver(PowerObserver* obs) {
   observers_->RemoveObserver(obs);
 }
 
-void PowerMonitor::ProcessPowerEvent(PowerEvent event_id) {
-  // Suppress duplicate notifications.  Some platforms may
-  // send multiple notifications of the same event.
-  switch (event_id) {
-    case POWER_STATE_EVENT:
-      {
-        bool on_battery = IsBatteryPower();
-        if (on_battery != battery_in_use_) {
-          battery_in_use_ = on_battery;
-          NotifyPowerStateChange();
-        }
-      }
-      break;
-    case RESUME_EVENT:
-      if (suspended_) {
-        suspended_ = false;
-        NotifyResume();
-      }
-      break;
-    case SUSPEND_EVENT:
-      if (!suspended_) {
-        suspended_ = true;
-        NotifySuspend();
-      }
-      break;
-  }
+PowerMonitorSource* PowerMonitor::Source() {
+  return source_.get();
 }
 
-void PowerMonitor::BatteryCheck() {
-  ProcessPowerEvent(PowerMonitor::POWER_STATE_EVENT);
+bool PowerMonitor::BatteryPower() {
+  return source_->BatteryPower();
 }
 
-void PowerMonitor::NotifyPowerStateChange() {
-  DVLOG(1) << "PowerStateChange: " << (BatteryPower() ? "On" : "Off")
+void PowerMonitor::NotifyPowerStateChange(bool battery_in_use) {
+  DVLOG(1) << "PowerStateChange: " << (battery_in_use ? "On" : "Off")
            << " battery";
-  observers_->Notify(&PowerObserver::OnPowerStateChange, BatteryPower());
+  observers_->Notify(&PowerObserver::OnPowerStateChange, battery_in_use);
 }
 
 void PowerMonitor::NotifySuspend() {