Replace IPC messages in layout_test_render_frame_observer.

content/shell/common/layout_test.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.
+
+module content.mojom;
+
+[Native]
+struct ShellTestConfig;
+
+interface LayoutTestControl {
+  // Asks a frame to dump its contents into a string and send them back over
+  // IPC.
+  LayoutDumpRequest();
+
+  // Replicates test config (for an already started test) to a new renderer
+  // that hosts parts of the main test window.
+  ReplicateTestConfiguration(ShellTestConfig config);
+
+  // Sets the test config for a layout test that is being started.  This message
+  // is sent only to a renderer that hosts parts of the main test window.
+  SetTestConfiguration(ShellTestConfig config);
+
+  // Sets up a secondary renderer (renderer that doesn't [yet] host parts of the
+  // main test window) for a layout test.
+  SetupSecondaryRenderer();
+};