Add Ctrl+Alt+H as global shortcut to toggle high contrast mode.

ash/common/accelerators/accelerator_controller.cc

Index: ash/common/accelerators/accelerator_controller.cc
diff --git a/ash/common/accelerators/accelerator_controller.cc b/ash/common/accelerators/accelerator_controller.cc
index 080315a496d03c481ef131ff4f91fb6f7348b9c6..aa8bcf0573b83f1d71afcfe1d39df6d2c34ccccb 100644
--- a/ash/common/accelerators/accelerator_controller.cc
+++ b/ash/common/accelerators/accelerator_controller.cc
@@ -466,6 +466,12 @@ void HandleToggleCapsLock() {
   keyboard->SetCapsLockEnabled(!keyboard->CapsLockIsEnabled());
 }
 
+void HandleToggleHighContrast() {
+  base::RecordAction(UserMetricsAction("Accel_Toggle_High_Contrast"));
+
+  WmShell::Get()->accessibility_delegate()->ToggleHighContrast();
+}
+
 void HandleToggleSpokenFeedback() {
   base::RecordAction(UserMetricsAction("Accel_Toggle_Spoken_Feedback"));
 
@@ -826,6 +832,7 @@ bool AcceleratorController::CanPerformAction(
     case OPEN_GET_HELP:
     case SHOW_IME_MENU_BUBBLE:
     case SUSPEND:
+    case TOGGLE_HIGH_CONTRAST:
     case TOGGLE_SPOKEN_FEEDBACK:
     case TOGGLE_WIFI:
     case VOLUME_DOWN:
@@ -1043,6 +1050,9 @@ void AcceleratorController::PerformAction(AcceleratorAction action,
     case TOGGLE_CAPS_LOCK:
       HandleToggleCapsLock();
       break;
+    case TOGGLE_HIGH_CONTRAST:
+      HandleToggleHighContrast();
+      break;
     case TOGGLE_SPOKEN_FEEDBACK:
       HandleToggleSpokenFeedback();
       break;