Show ChromeVox caption panel when spoken feedback is enabled.

ash/default_accessibility_delegate.cc

Index: ash/default_accessibility_delegate.cc
diff --git a/ash/default_accessibility_delegate.cc b/ash/default_accessibility_delegate.cc
index f337a2eb39a3cc51ddd641446acbf76ca32c8bd0..3fb9430af8c054fc654328d019f156ed7a2aa64b 100644
--- a/ash/default_accessibility_delegate.cc
+++ b/ash/default_accessibility_delegate.cc
@@ -118,4 +118,9 @@ base::TimeDelta DefaultAccessibilityDelegate::PlayShutdownSound() const {
   return base::TimeDelta();
 }
 
+gfx::Insets DefaultAccessibilityDelegate::GetWorkAreaInsets(
+    aura::Window* root_window) const {
+  return gfx::Insets();
+}
+
 }  // namespace ash