arc-app-launcher: Minimal support for ARC app launcher.

components/arc/common/arc_instance_messages.h

 // 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.
 
 // Messages sent from the host to the ARC instance.
 // Multiply-included message file, hence no include guard.
 
 #include <stdint.h>
 
+#include <string>
+
 #include "base/file_descriptor_posix.h"
 #include "ipc/ipc_message_macros.h"
 
 #define IPC_MESSAGE_START ArcInstanceMsgStart
 
 // Registers a virtual input device on the container side.
 // |name| is the device name, like "Chrome OS Keyboard".
 // |device_type| is the device type, like "keyboard".
 // The virtual device will be reading 'struct input_event's from |fd|.  The
 // ownership of |fd| will be transferred to the receiver, so the sender must
 // not close it.
 IPC_MESSAGE_CONTROL3(ArcInstanceMsg_RegisterInputDevice,
                      std::string, /* name */
                      std::string, /* device_type */
                      base::FileDescriptor /* fd */)
+
+// Sends a request to ARC to refresh list of ARC apps.
+// ArcInstanceMsg_RefreshApps is expected in response to this message. However,
+// response may not be sent if ARC is not ready yet (boot completed event is
+// not received).
+IPC_MESSAGE_CONTROL0(ArcInstanceMsg_RefreshApps)
+
+// Sends a request to ARC to launch an ARC app defined by |package| and
+// |activity|, which cannot be empty.
+IPC_MESSAGE_CONTROL2(ArcInstanceMsg_LaunchApp,
+                     std::string, /* package */
+                     std::string /* activity */)
+
+// It sends a request to ARC for the ARC app icon of a required scale factor.

[elijahtaylor (use chromium), 2015/11/19 05:52:00]

nit: remove "It"?

[khmel1, 2015/11/19 17:11:41]

Done.

+// Scale factor is an enum defined at ui/base/layout.h. App is defined by
+// package and activity, which cannot be empty.
+IPC_MESSAGE_CONTROL3(ArcInstanceMsg_RequestIcon,
+                     std::string, /* package */
+                     std::string, /* activity */
+                     int /* scale factor */)