Support Shift+Search+Arrows to navigate and Control to silence speech everywhere

ash/shell/shell_delegate_impl.cc

Index: ash/shell/shell_delegate_impl.cc
diff --git a/ash/shell/shell_delegate_impl.cc b/ash/shell/shell_delegate_impl.cc
index 25d092a94ec62d7c1e9e39b45af1052720edaa64..c40ca38fdd939f02ebc99b7dd7a0cede27bdbba0 100644
--- a/ash/shell/shell_delegate_impl.cc
+++ b/ash/shell/shell_delegate_impl.cc
@@ -175,6 +175,9 @@ bool ShellDelegateImpl::ShouldAlwaysShowAccessibilityMenu() const {
   return false;
 }
 
+void ShellDelegateImpl::SilenceSpokenFeedback() const {
+}
+
 app_list::AppListViewDelegate* ShellDelegateImpl::CreateAppListViewDelegate() {
   return ash::shell::CreateAppListViewDelegate();
 }