Show ChromeVox caption panel when spoken feedback is enabled.

ash/accessibility_delegate.h

Index: ash/accessibility_delegate.h
diff --git a/ash/accessibility_delegate.h b/ash/accessibility_delegate.h
index cb821c8ad0a4eb1025b9f4a4a3381a2d599a7a09..0e8b1f5b6bb7b3a84288975ad27eb993aed8b77d 100644
--- a/ash/accessibility_delegate.h
+++ b/ash/accessibility_delegate.h
@@ -8,6 +8,11 @@
 #include "ash/ash_export.h"
 #include "base/time/time.h"
 #include "ui/chromeos/accessibility_types.h"
+#include "ui/gfx/geometry/insets.h"
+
+namespace aura {
+class Window;
+}
 
 namespace ash {
 
@@ -88,6 +93,10 @@ class ASH_EXPORT AccessibilityDelegate {
 
   // Initiates play of shutdown sound and returns it's duration.
   virtual base::TimeDelta PlayShutdownSound() const = 0;
+
+  // Get work area insets due to accessibility overlays on one of the
+  // screen edges, for the given root window.
+  virtual gfx::Insets GetWorkAreaInsets(aura::Window* root_window) const = 0;
 };
 
 }  // namespace ash