Add placeholder for RWHVChildFrame::CreateBrowserAccessibilityManager.

content/browser/frame_host/render_widget_host_view_child_frame.cc

Index: content/browser/frame_host/render_widget_host_view_child_frame.cc
diff --git a/content/browser/frame_host/render_widget_host_view_child_frame.cc b/content/browser/frame_host/render_widget_host_view_child_frame.cc
index 91b695bff7e2d514b2d887584d2459ad649dc590..5c4199c5338632d277c278a63ac578005883f86e 100644
--- a/content/browser/frame_host/render_widget_host_view_child_frame.cc
+++ b/content/browser/frame_host/render_widget_host_view_child_frame.cc
@@ -336,4 +336,12 @@ SkColorType RenderWidgetHostViewChildFrame::PreferredReadbackFormat() {
   return kN32_SkColorType;
 }
 
+BrowserAccessibilityManager*
+RenderWidgetHostViewChildFrame::CreateBrowserAccessibilityManager(
+    BrowserAccessibilityDelegate* delegate) {
+  // This eventually needs to be implemented for cross-process iframes.
+  // http://crbug.com/368298
+  return NULL;
+}
+
 }  // namespace content