Allow createLocalChild to specify previous sibling frame.

Source/web/WebFrame.cpp

Index: Source/web/WebFrame.cpp
diff --git a/Source/web/WebFrame.cpp b/Source/web/WebFrame.cpp
index ca855dca8a7f4a72e69996046ad8a91ae3dffd39..c4704ff90f861d82da94e5edf4f7dd071cf65d8d 100644
--- a/Source/web/WebFrame.cpp
+++ b/Source/web/WebFrame.cpp
@@ -142,6 +142,33 @@ void WebFrame::setOpener(WebFrame* opener)
     m_opener = opener;
 }
 
+void WebFrame::insertAfter(WebFrame* newChild, WebFrame* previousSibling)
+{
+    newChild->m_parent = this;
+
+    WebFrame* next;
+    if (!previousSibling) {
+        // Insert at the beginning if no previous sibling is specified.
+        next = m_firstChild;
+        m_firstChild = newChild;
+    } else {
+        ASSERT(previousSibling->m_parent == this);
+        next = previousSibling->m_nextSibling;
+        previousSibling->m_nextSibling = newChild;
+        newChild->m_previousSibling = previousSibling;
+    }
+
+    if (next) {
+        newChild->m_nextSibling = next;
+        next->m_previousSibling = newChild;
+    } else {
+        m_lastChild = newChild;
+    }
+
+    toCoreFrame(this)->tree().invalidateScopedChildCount();
+    toCoreFrame(this)->host()->incrementSubframeCount();
+}
+
 void WebFrame::appendChild(WebFrame* child)
 {

[dcheng, 2015/05/01 23:39:36]

Should we re-express this in terms of insertAfter()?

[alexmos, 2015/05/02 00:21:45]

Done.  Thanks for reminding me to do it!  Any thoughts on what to do  with the
FIXME?  I don't know the context, so I've kept it for now.

[dcheng, 2015/05/04 17:30:36]

The original check was to make sure we didn't accidentally appendChild a frame
that belonged to another page. I guess we could ASSERT that the value of
WebFrame::view() is the same.

[alexmos, 2015/05/04 21:38:54]

Hmm, that doesn't seem to work, because we call insertAfter() before we
initialize the new child's core frame, so the new child's view() is null.  I'll
leave the assert as-is for now.

     // FIXME: Original code asserts that the frames have the same Page. We