Bug 1550811. Back out the second part of the fix for bug 325352 until we have a fix for the crash issues it causes. r=hsivonen

Differential Revision: https://phabricator.services.mozilla.com/D30682

--HG--
extra : moz-landing-system : lando

dom/html/nsHTMLDocument.cpp

@@ -1015,23 +1015,25 @@ Document* nsHTMLDocument::Open(const Optional<nsAString>& /* unused */,
     return nullptr;
   }
 
-  // Step 5 -- if we have an active parser with a nonzero script nesting level,
-  // just no-op.
-  //
-  // If we have a parser that has a zero script nesting level, we need to
-  // properly terminate it before setting up a new parser.  See the similar code
-  // in WriteCommon that handles the !IsInsertionPointDefined() case and should
-  // stay in sync with this code.
-  if (mParser && !mParser->HasNonzeroScriptNestingLevel()) {
-    // Make sure we don't re-enter.
-    IgnoreOpensDuringUnload ignoreOpenGuard(this);
-    mParser->Terminate();
-    MOZ_RELEASE_ASSERT(!mParser, "mParser should have been null'd out");
-  }
-
-  // The mParserAborted check here is probably wrong.  Removing it is
-  // tracked in https://bugzilla.mozilla.org/show_bug.cgi?id=1475000
+  // Step 5 -- if we have an active parser, just no-op.
+  // If we already have a parser we ignore the document.open call.
   if (mParser || mParserAborted) {
+    // The WHATWG spec used to say: "If the document has an active parser that
+    // isn't a script-created parser, and the insertion point associated with
+    // that parser's input stream is not undefined (that is, it does point to
+    // somewhere in the input stream), then the method does nothing. Abort these
+    // steps and return the Document object on which the method was invoked."
+    // Note that aborting a parser leaves the parser "active" with its insertion
+    // point "not undefined". We track this using mParserAborted, because
+    // aborting a parser nulls out mParser.
+    //
+    // Actually, the spec says something slightly different now, about having
+    // an "active parser whose script nesting level is greater than 0".  It
+    // does not mention insertion points at all.  Not sure whether it matters
+    // in practice.  It seems like "script nesting level" replaced the
+    // insertion point concept?  Anyway,
+    // https://bugzilla.mozilla.org/show_bug.cgi?id=1475000 is probably
+    // relevant here.
     return this;
   }
 
@@ -1321,9 +1323,7 @@ void nsHTMLDocument::WriteCommon(const nsAString& aText, bool aNewlineTerminate,
       return;
     }
     // The spec doesn't tell us to ignore opens from here, but we need to
-    // ensure opens are ignored here.  See similar code in Open() that handles
-    // the case of an existing parser which is not currently running script and
-    // should stay in sync with this code.
+    // ensure opens are ignored here.
     IgnoreOpensDuringUnload ignoreOpenGuard(this);
     mParser->Terminate();
     MOZ_RELEASE_ASSERT(!mParser, "mParser should have been null'd out");

testing/web-platform/tests/html/webappapis/dynamic-markup-insertion/opening-the-input-stream/parser-no-script-nesting.window.js

@@ -1,18 +0,0 @@
-async_test(t => {
-  const frame = document.createElement("iframe");
-  frame.onload = t.step_func_done(() => {
-    frame.onload = null;
-    const doc = frame.contentDocument;
-
-    // Each open() call should reset the DOM for the document, because even
-    // though there is a live parser, that parser's script insertion level is 0.
-    for (var i = 0; i < 5; ++i) {
-      doc.open();
-      doc.write("hello");
-    }
-    doc.close()
-    assert_equals(doc.documentElement.textContent, "hello");
-  });
-  t.add_cleanup(() => frame.remove());
-  document.body.appendChild(frame);
-}, "open() should reset the DOM even if there's an active parser, if that parser's script insertion level is 0");