Extract content dependency from keyboard code

ash/content/shell_content_state.cc

 // Copyright 2015 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "ash/content/shell_content_state.h"
 
 #include "base/logging.h"
+#include "ui/keyboard/content/keyboard.h"
 
 namespace ash {
 
 // static
 ShellContentState* ShellContentState::instance_ = nullptr;
 
 // static
 void ShellContentState::SetInstance(ShellContentState* instance) {
   DCHECK(!instance_);
   instance_ = instance;
 }
 
 // static
 ShellContentState* ShellContentState::GetInstance() {
   DCHECK(instance_);
   return instance_;
 }
 
 // static
 void ShellContentState::DestroyInstance() {
   DCHECK(instance_);
   delete instance_;
   instance_ = nullptr;
 }
 
-ShellContentState::ShellContentState() {}
+ShellContentState::ShellContentState() {
+// The keyboard system must be initialized before the RootWindowController is
+// created.
+#if defined(OS_CHROMEOS)
+  keyboard::InitializeKeyboard();
+#endif
+}
 ShellContentState::~ShellContentState() {}
 
 }  // namespace ash