OopAsh: Bail on Shell::EnableKeyboard in Mash and OopAsh.

ShellDelegateMash does not create a valid keyboard ui instance.

TBR=blakeo@chromium.org

Bug: 856235, 646565
Test: No keyboard crash on --enable-features=OopAsh device startup.
Change-Id: I26ac1c13f46b839a4b77c6aaf478abec745126f1
Reviewed-on: https://chromium-review.googlesource.com/1119088
Commit-Queue: Michael Wasserman <msw@chromium.org>
Reviewed-by: Michael Wasserman <msw@chromium.org>
Reviewed-by: James Cook <jamescook@chromium.org>
Cr-Commit-Position: refs/heads/master@{#571313}

ash/shell.cc

@@ -491,11 +491,16 @@ void Shell::EnableKeyboard() {
     for (auto* const controller : GetAllRootWindowControllers())
       controller->DeactivateKeyboard(keyboard_controller_.get());
   }
-  keyboard_controller_->EnableKeyboard(shell_delegate_->CreateKeyboardUI(),
+
+  // TODO(crbug.com/646565): ShellDelegateMash does not support keyboard ui yet.
+  auto keyboard_ui = shell_delegate_->CreateKeyboardUI();
+  if (!keyboard_ui && !::features::IsAshInBrowserProcess())
+    return;
+
+  keyboard_controller_->EnableKeyboard(std::move(keyboard_ui),
                                        virtual_keyboard_controller_.get());
   for (auto& observer : shell_observers_)
     observer.OnKeyboardControllerCreated();
-
   GetPrimaryRootWindowController()->ActivateKeyboard(
       keyboard_controller_.get());
 }

ui/keyboard/keyboard_controller.cc

@@ -182,6 +182,7 @@ void KeyboardController::EnableKeyboard(std::unique_ptr<KeyboardUI> ui,
     DisableKeyboard();
 
   ui_ = std::move(ui);
+  DCHECK(ui_);
 
   layout_delegate_ = delegate;
   show_on_content_update_ = false;