Allow createLocalChild to specify previous sibling frame.

Source/web/WebRemoteFrameImpl.cpp

Index: Source/web/WebRemoteFrameImpl.cpp
diff --git a/Source/web/WebRemoteFrameImpl.cpp b/Source/web/WebRemoteFrameImpl.cpp
index 5e5b42a42629b83fad028a9b2b38fb46ecddc7d1..22ea043eb00c4b8850a27461a2aa8c0fda35c61a 100644
--- a/Source/web/WebRemoteFrameImpl.cpp
+++ b/Source/web/WebRemoteFrameImpl.cpp
@@ -714,12 +714,18 @@ WebString WebRemoteFrameImpl::layerTreeAsText(bool showDebugInfo) const
     return WebString();
 }
 
+// TODO(alexmos): Remove once Chromium side is updated to take previous sibling.
 WebLocalFrame* WebRemoteFrameImpl::createLocalChild(const WebString& name, WebSandboxFlags sandboxFlags, WebFrameClient* client)
 {
+    return createLocalChild(name, sandboxFlags, client, lastChild());
+}
+
+WebLocalFrame* WebRemoteFrameImpl::createLocalChild(const WebString& name, WebSandboxFlags sandboxFlags, WebFrameClient* client, WebFrame* previousSibling)
+{
     WebLocalFrameImpl* child = toWebLocalFrameImpl(WebLocalFrame::create(client));
     WillBeHeapHashMap<WebFrame*, OwnPtrWillBeMember<FrameOwner>>::AddResult result =
         m_ownersForChildren.add(child, RemoteBridgeFrameOwner::create(child, static_cast<SandboxFlags>(sandboxFlags)));
-    appendChild(child);
+    insertAfter(child, previousSibling);
     // FIXME: currently this calls LocalFrame::init() on the created LocalFrame, which may
     // result in the browser observing two navigations to about:blank (one from the initial
     // frame creation, and one from swapping it into the remote process). FrameLoader might