Adds special support to the device manager for keyboards devices.

ui/events/input_device.cc

Index: ui/events/input_device.cc
diff --git a/ui/events/input_device.cc b/ui/events/input_device.cc
new file mode 100644
index 0000000000000000000000000000000000000000..26fca7fc1d1e45517db5c35ef782f70a3d98daa5
--- /dev/null
+++ b/ui/events/input_device.cc
@@ -0,0 +1,20 @@
+// Copyright 2014 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 "ui/events/input_device.h"
+
+#include <string>
+
+namespace ui {
+
+// static
+const int InputDevice::kInvalidId = 0;
+
+InputDevice::InputDevice(
+    int id,

[sky, 2014/10/20 22:18:44]

It's not readily obvious that the id is unique between all input types. But that
appears to be the case. Please document it.

+    InputDeviceType type,
+    const std::string& name) : id(id), type(type), name(name) {
+}
+
+}  // namespace ui