Bug 1361041: Avoid posting ReconstructFrame hints to an uninitialized PresShell. r=bz

The call that's causing the crash seems to be [1], that is, we're trying to
recreate frames for the root element, which should always have a frame created
at the initialization of the PresShell.

So the function I removed in that bug had something like the following:

  if (!mDidInitialize) {
    // Nothing to do here.  In fact, if we proceed and aContent is the
    // root we will crash.
    return NS_OK;
  }

Which PostRecreateFramesFor doesn't guard against (because I thought it was not
needed, per tryserver results).

Sounds a lot like we do need that check, though I'd like to have a testcase
where it happens :(

[1]: http://searchfox.org/mozilla-central/rev/3dc6ceb42746ab40f1441e1e659ffb8f62ae78e3/layout/base/nsCSSFrameConstructor.cpp#2420

MozReview-Commit-ID: Lh6SohNmmI6

--HG--
extra : rebase_source : 5b7076f86d41f5489e47ca16ac2f3620812ee9e8

layout/base/PresShell.cpp

@@ -2954,6 +2954,12 @@ PresShell::CreateFramesFor(nsIContent* aContent)
 void
 nsIPresShell::PostRecreateFramesFor(Element* aElement)
 {
+  if (MOZ_UNLIKELY(!mDidInitialize)) {
+    // Nothing to do here. In fact, if we proceed and aElement is the root, we
+    // will crash.
+    return;
+  }
+
   mPresContext->RestyleManager()->PostRestyleEvent(aElement, nsRestyleHint(0),
                                                    nsChangeHint_ReconstructFrame);
 }