Implement High Contrast mode for Chrome OS

ash/shell_delegate.h

Index: ash/shell_delegate.h
diff --git a/ash/shell_delegate.h b/ash/shell_delegate.h
index 43c15936b0353c115368b5e3f9d663c52325402c..f9545fe970d4e48f8c5bb063dc488401c284ddcd 100644
--- a/ash/shell_delegate.h
+++ b/ash/shell_delegate.h
@@ -78,6 +78,9 @@ class ASH_EXPORT ShellDelegate {
   // for accessibility.
   virtual void ToggleSpokenFeedback() = 0;
 
+  // Check if High Contrast mode is enabled.
+  virtual bool IsHighContrastEnabled() = 0;
+
   // Invoked to create an AppListViewDelegate. Shell takes the ownership of
   // the created delegate.
   virtual AppListViewDelegate* CreateAppListViewDelegate() = 0;