arc: enable Android tracing from chrome://tracing in dev mode

components/arc/common/tracing.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 TracingInstance {
+  // Queries available tracing categories in the container.
+  QueryAvailableCategories@0() => (array<string> categories);
+
+  // 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);
+};