Why this CL triggers an OilPan crash.

content/common/renderer.mojom

 // Copyright 2016 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;
 
 import "content/common/native_types.mojom";
 import "ipc/ipc.mojom";
 import "ui/gfx/geometry/mojo/geometry.mojom";
 import "ui/gfx/mojo/icc_profile.mojom";
@@ skipping 14 matching lines @@
   // The ID of the widget for the main frame.
   int32 main_frame_widget_routing_id = IPC.mojom.kRoutingIdNone;
 
   // The session storage namespace ID this view should use.
   int64 session_storage_namespace_id;
 
   // The route ID of the opener RenderFrame or RenderFrameProxy, if we need to
   // set one (MSG_ROUTING_NONE otherwise).
   int32 opener_frame_route_id = IPC.mojom.kRoutingIdNone;
 
+  // Id of a related set of browsing contexts that the new view should belong
+  // to.
+  int32 browsing_instance_id;
+
   // Whether the RenderView should initially be swapped out.
   bool swapped_out;
 
   // Carries replicated information, such as frame name and sandbox flags, for
   // this view's main frame, which will be a proxy in |swapped_out|
   // views when in --site-per-process mode, or a RenderFrame in all other
   // cases.
   FrameReplicationState replicated_frame_state;
 
   // The ID of the proxy object for the main frame in this view. It is only
@@ skipping 121 matching lines @@
   UpdateScrollbarTheme(UpdateScrollbarThemeParams params);
 
   // Notification that the OS X Aqua color preferences changed.
   OnSystemColorsChanged(int32 aqua_color_variant, string highlight_text_color,
                         string highlight_color);
 
   // Tells the renderer to empty its plugin list cache, optional reloading
   // pages containing plugins.
   PurgePluginListCache(bool reload_pages);
 };