Really fix #3738 by only processing iframe src attributes during parsing.

components/script/dom/htmliframeelement.rs

@@ -121,7 +121,7 @@ impl<'a> HTMLIFrameElementHelpers for JSRef<'a, HTMLIFrameElement> {
         }));
 
         let doc = document_from_node(self).root();
-        if doc.ReadyState() != DocumentReadyStateValues::Complete {
+        if doc.ReadyState() == DocumentReadyStateValues::Loading {
             // https://github.com/servo/servo/issues/3738
             // We can't handle dynamic frame tree changes in the compositor right now.
             let ConstellationChan(ref chan) = page.constellation_chan;

tests/html/test-iframe.html

@@ -0,0 +1,2 @@
+<iframe id="whee"></iframe>
+<script>document.getElementById('whee').src = "http://google.com"</script>

tests/wpt/metadata/XMLHttpRequest/open-url-javascript-window-2.htm.ini

@@ -1,3 +1,5 @@
 [open-url-javascript-window-2.htm]
   type: testharness
-  expected: CRASH
+  expected: TIMEOUT
+  [XMLHttpRequest: open() - resolving URLs (javascript: ]
+    expected: TIMEOUT

tests/wpt/metadata/XMLHttpRequest/open-url-javascript-window.htm.ini

@@ -1,3 +1,5 @@
 [open-url-javascript-window.htm]
   type: testharness
-  expected: CRASH
+  expected: TIMEOUT
+  [XMLHttpRequest: open() - resolving URLs (javascript: ]
+    expected: TIMEOUT

tests/wpt/metadata/dom/nodes/Document-createElement-namespace.html.ini

@@ -1,3 +1,3 @@
 [Document-createElement-namespace.html]
   type: testharness
-  expected: CRASH
+  expected: TIMEOUT

tests/wpt/metadata/html/browsers/browsing-the-web/read-text/load-text-plain.html.ini

@@ -1,3 +1,9 @@
 [load-text-plain.html]
   type: testharness
-  expected: CRASH
+  expected: TIMEOUT
+  [Checking document metadata for text file]
+    expected: NOTRUN
+  [Checking DOM for text file]
+    expected: NOTRUN
+  [Checking contents for text file]
+    expected: NOTRUN

tests/wpt/metadata/html/infrastructure/urls/terminology-0/document-base-url.html.ini

@@ -1,3 +1,3 @@
 [document-base-url.html]
   type: testharness
-  expected: CRASH
+  expected: TIMEOUT

tests/wpt/metadata/old-tests/submission/Opera/script_scheduling/039.html.ini

@@ -1,3 +1,4 @@
 [039.html]
   type: testharness
-  expected: CRASH
+  [ scheduler: IFRAMEs added with DOM]
+    expected: FAIL