Create a new RenderFrameHost per child frame when --site-per-process is enabled.

content/common/frame_messages.h

+// Copyright (c) 2013 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.
+
+// IPC messages for interacting with frames.
+// Multiply-included message file, hence no include guard.
+
+#include "content/common/content_export.h"
+#include "ipc/ipc_message_macros.h"
+
+#undef IPC_MESSAGE_EXPORT
+#define IPC_MESSAGE_EXPORT CONTENT_EXPORT
+
+#define IPC_MESSAGE_START FrameMsgStart
+
+// Sent by the renderer when a child frame is created in the renderer. The
+// |parent_frame_id| and |frame_id| are NOT routing ids. They are
+// renderer-allocated identifiers used for tracking a frame's creation.
+//
+// Each of these messages will have a corresponding FrameHostMsg_Detach message
+// sent when the frame is detached from the DOM.
+//
+// TOOD(ajwong): replace parent_render_frame_id and frame_id with just the
+// routing ids.
+IPC_SYNC_MESSAGE_CONTROL4_1(FrameHostMsg_CreateChildFrame,
+                            int32 /* parent_render_frame_id */,
+                            int64 /* parent_frame_id */,
+                            int64 /* frame_id */,
+                            std::string /* frame_name */,
+                            int /* new_render_frame_id */)
+
+// Sent by the renderer to the parent RenderFrameHost when a child frame is
+// detached from the DOM.
+IPC_MESSAGE_ROUTED2(FrameHostMsg_Detach,
+                    int64 /* parent_frame_id */,
+                    int64 /* frame_id */)
+