add voice interaction shortcut.

components/arc/common/voice_interaction.mojom

+// Copyright 2017 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.
+//
+// Next MinVersion: 1
+
+module arc.mojom;
+
+// Represents view structure to be passed to ARC. The view
+// structure is synthesized from the AXStructure, which
+// is a simplified representation of the DOM tree. We
+// map each node of the AXStructure into a view element.
+struct VoiceInteractionStructure {
+  // Whether this is a valid response
+  bool success;

[hidehiko, 2017/03/10 06:14:50]

Is there a case that only some part of children has "success = false"?
If so it's good to be noted here with when it happens.
If not, probably instead of the member here, the method signature will be,
either;

- GetVoiceInteractionStructure@1() => (bool success, VoiceInteractionStructure
structure);
- GetVoiceInteractionStructure@1() => (Status status, VoiceInteractionStructure
structure); // status represent success or error code incl reason., or
- GetVoiceInteractionStructure@1() => (VoiceInteractionStructure? structure); 
// return null structure on failure.

or something?

[Muyuan, 2017/03/10 22:36:10]

Sure. How about using Optional<T> for this?

[Luis Héctor Chávez, 2017/03/13 17:39:34]

Optional<T> makes more sense.

+
+  // Geometry of the view in pixels
+  int32 x;
+  int32 y;
+  int32 width;
+  int32 height;
+
+  // Text of the view in utf-16 encoding

[hidehiko, 2017/03/10 06:14:50]

Could you comment the reason why uint8 is used to store utf-16? Also, maybe
endian if it is not trivial, too?

[Muyuan, 2017/03/10 22:36:10]

In Chromium, strings seem to be always little endian (verified on minnie). Also
it seems that all strings in AXStructure are string16, but I can't seem to pass
string16 directly through mojo calls.

+  array<uint8> text;
+
+  // Text properties
+  float text_size;
+  int32 color;
+  int32 bgcolor;
+  bool bold;
+  bool italic;
+  bool underline;
+  bool line_through;
+
+  // Is the text selected
+  bool has_selection;
+  // Start and end position of the selection, inclusive.

[hidehiko, 2017/03/10 06:14:50]

Because of inconsistency of encoding "utf-16" and the storage "uint8", could you
comment the index is for which?

[Muyuan, 2017/03/10 22:36:10]

Done.

+  int32 start_selection;
+  int32 end_selection;
+
+  // Fake Android view class name of the element.  Each node is assigned
+  // a closest approximation of Android's views.
+  string class_name;
+
+  // Children of current node
+  array<VoiceInteractionStructure> children;
+};
+
+// Handles voice interaction queries from Android.
+// Next method ID: 2
+interface VoiceInteractionHost {
+  CaptureFocusedWindow@0() => (array<uint8> png_data);

[hidehiko, 2017/03/10 06:14:50]

because mojo is an interface between Chrome and ARC instance,
could you comment what these methods do and their responsibility explicitly as
document?

[Muyuan, 2017/03/10 22:36:10]

Done.

+  GetVoiceInteractionStructure@1() => (VoiceInteractionStructure structure);
+};
+
+// Connects with Android system server.
+// Next method ID:2
+interface VoiceInteractionCaptureInstance {
+  Init@0(VoiceInteractionHost host_ptr);
+  StartVoiceInteractionSession@1();
+};
+
+// Connects with ArcHome.
+// Next method ID: 1
+interface VoiceInteractionArcHomeInstance {
+  Init@0(VoiceInteractionHost host_ptr);
+};
+
+