Implement Linux IME support

mojo/services/keyboard/interfaces/keyboard.mojom

 // 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.
 
 [DartPackage="mojo_services"]
 module keyboard;
 
+import "native_viewport/interfaces/native_viewport.mojom";
+
 struct CompletionData {
   int64 id;
   int32 position;
   string text;
   string label;
 };
 
 struct CorrectionData {
   int32 offset;
   string old_text;
@@ skipping 24 matching lines @@
   DATETIME,
 };
 
 interface KeyboardService {
   Show(KeyboardClient client, KeyboardType type);
   ShowByRequest();
   Hide();
   SetText(string text);
   SetSelection(int32 start, int32 end);
 };
+
+interface KeyboardServiceFactory {
+  CreateKeyboardService(
+      mojo.NativeViewportEventDispatcher& keyEventDispatcher,
+      KeyboardService& serviceRequest);
+};