arc: enable Android tracing in verified-boot mode

components/arc/common/trace.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;
+
+interface TraceInstance {
+  // Queries available tracing categories in the container.
+  QueryAvailableCategories@0() => (array<string> categories);
+
+  // Sets host socket handler for client to send trace events back to the host.
+  // The host is required to call this function before starting tracing.
+  SetHostSocket@3(handle sock);

[Luis Héctor Chávez, 2017/02/10 17:43:55]

Why not send this in StartTracing()?

[Earl Ou, 2017/02/16 09:56:46]

I think we don't need to recreate the socket between host and client every time
we start tracing. It's only called one time after the bridge is ready.

[Earl Ou, 2017/03/22 11:38:26]

Move this to StartTracing now.

+
+  // Starts tracing in the container with the given categories.
+  StartTracing@1(array<string> categories) => (bool success);
+
+  // Stops tracing in the container.
+  StopTracing@2() => (bool success);
+};