Explicitly initialize secondary renderers for layout tests.

content/shell/common/shell_messages.h

 // Copyright (c) 2012 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.
 
 // Multiply-included file, no traditional include guard.
 #include <string>
 #include <vector>
 
 #include "base/values.h"
 #include "content/public/common/common_param_traits.h"
@@ skipping 18 matching lines @@
 IPC_STRUCT_TRAITS_MEMBER(initial_size)
 IPC_STRUCT_TRAITS_END()
 
 // Tells the renderer to reset all test runners.
 IPC_MESSAGE_ROUTED0(ShellViewMsg_Reset)
 
 // Sets the path to the WebKit checkout.
 IPC_MESSAGE_CONTROL1(ShellViewMsg_SetWebKitSourceDir,
                      base::FilePath /* webkit source dir */)
 
-// Sets the test config for a layout test that is being started.
+// 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.
 IPC_MESSAGE_ROUTED1(ShellViewMsg_SetTestConfiguration,
                     content::ShellTestConfiguration)
 
-// Replicates test config (for an already started test) to a new renderer.
+// Replicates test config (for an already started test) to a new renderer
+// that hosts parts of the main test window.
 IPC_MESSAGE_ROUTED2(
     ShellViewMsg_ReplicateTestConfiguration,
     content::ShellTestConfiguration,
     base::DictionaryValue /* accumulated_layout_test_runtime_flags_changes */)
 
+// Sets up a secondary renderer (renderer that doesn't [yet] host parts of the
+// main test window) for a layout test.
+IPC_MESSAGE_ROUTED0(ShellViewMsg_SetupSecondaryRenderer)
+
 // Used to broadcast changes happening in one renderer to all other renderers.
 IPC_MESSAGE_ROUTED1(
     ShellViewMsg_ReplicateLayoutTestRuntimeFlagsChanges,
     base::DictionaryValue /* changed_layout_test_runtime_flags */)
 
 // Tells the main window that a secondary renderer in a different process thinks
 // the test is finished.
 IPC_MESSAGE_ROUTED0(ShellViewMsg_NotifyDone)
 
 // Pushes a snapshot of the current session history from the browser process.
@@ skipping 81 matching lines @@
                     content::LeakDetectionResult /* result */)
 
 IPC_MESSAGE_ROUTED1(ShellViewHostMsg_SetBluetoothManualChooser,
                     bool /* enable */)
 IPC_MESSAGE_ROUTED0(ShellViewHostMsg_GetBluetoothManualChooserEvents)
 IPC_MESSAGE_ROUTED1(ShellViewMsg_ReplyBluetoothManualChooserEvents,
                     std::vector<std::string> /* events */)
 IPC_MESSAGE_ROUTED2(ShellViewHostMsg_SendBluetoothManualChooserEvent,
                     std::string /* event */,
                     std::string /* argument */)