chromeos: Add power supply info reading capability

chrome/browser/chromeos/cros/power_library.h

Index: chrome/browser/chromeos/cros/power_library.h
diff --git a/chrome/browser/chromeos/cros/power_library.h b/chrome/browser/chromeos/cros/power_library.h
index e6ef46d0935746bf0869be3a7bcb9ba4dca79077..20f30acfa59cf6a35f965ebe417206b6df76770b 100644
--- a/chrome/browser/chromeos/cros/power_library.h
+++ b/chrome/browser/chromeos/cros/power_library.h
@@ -9,6 +9,7 @@
 // TODO(sque): Move to chrome/browser/chromeos/system, crosbug.com/16558
 
 #include "base/callback.h"
+#include "chrome/browser/chromeos/dbus/power_manager_client.h"
 
 namespace base {
 class TimeDelta;
@@ -17,6 +18,7 @@ class TimeDelta;
 namespace chromeos {
 
 typedef base::Callback<void(int64_t)> CalculateIdleTimeCallback;
+struct PowerStatus;
 
 struct PowerSupplyStatus {
   bool line_power_on;
@@ -36,12 +38,14 @@ struct PowerSupplyStatus {
                         battery_seconds_to_empty(0),
                         battery_seconds_to_full(0),
                         battery_percentage(0) {}
+
+  const std::string& ToString() const;
 };
 
 // This interface defines interaction with the ChromeOS power library APIs.
 // Classes can add themselves as observers. Users can get an instance of this
 // library class like this: chromeos::CrosLibrary::Get()->GetPowerLibrary()
-class PowerLibrary {
+class PowerLibrary : public PowerManagerClient::Observer {
  public:
   class Observer {
    public:
@@ -75,6 +79,10 @@ class PowerLibrary {
   // UI initiated request for status update.
   virtual void RequestStatusUpdate() = 0;
 
+  // Requests power supply info.
+  virtual void UpdatePowerStatus(const PowerStatus& status) = 0;
+
+
   // Factory function, creates a new instance and returns ownership.
   // For normal usage, access the singleton via CrosLibrary::Get().
   static PowerLibrary* GetImpl(bool stub);