Introducing ResumeLibrary to track system resume signal

chrome/browser/chromeos/status/clock_menu_button.cc

Index: chrome/browser/chromeos/status/clock_menu_button.cc
diff --git a/chrome/browser/chromeos/status/clock_menu_button.cc b/chrome/browser/chromeos/status/clock_menu_button.cc
index f285d281d77abef49990a35e5eca4761088d1942..12eb535b86a1fa6368c85a5b87cea947d0dd21d0 100644
--- a/chrome/browser/chromeos/status/clock_menu_button.cc
+++ b/chrome/browser/chromeos/status/clock_menu_button.cc
@@ -33,6 +33,7 @@ ClockMenuButton::ClockMenuButton(StatusAreaHost* host)
       host_(host) {
   // Add as SystemLibrary observer. We update the clock if timezone changes.
   CrosLibrary::Get()->GetSystemLibrary()->AddObserver(this);
+  CrosLibrary::Get()->GetPowerLibrary()->AddObserver(this);
 
   set_border(NULL);
   set_use_menu_button_paint(true);
@@ -45,6 +46,7 @@ ClockMenuButton::ClockMenuButton(StatusAreaHost* host)
 }
 
 ClockMenuButton::~ClockMenuButton() {
+  CrosLibrary::Get()->GetPowerLibrary()->RemoveObserver(this);
   CrosLibrary::Get()->GetSystemLibrary()->RemoveObserver(this);
 }
 
@@ -111,6 +113,13 @@ void ClockMenuButton::ActivatedAt(int index) {
 }
 
 ///////////////////////////////////////////////////////////////////////////////
+// ClockMenuButton, PowerLibrary::Observer implementation:
+
+void ClockMenuButton::SystemResumed() {
+  UpdateText();
+}
+
+///////////////////////////////////////////////////////////////////////////////
 // ClockMenuButton, SystemLibrary::Observer implementation:
 
 void ClockMenuButton::TimezoneChanged(const icu::TimeZone& timezone) {