Bug 1574016. Fix logic error in patch from bug 1547277. r=bradwerth

The fixed still worked because we get another SetBounds call right after with the same bounds. But it does mean we are doing some useless invalidation.

Differential Revision: https://phabricator.services.mozilla.com/D42059

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

layout/base/nsDocumentViewer.cpp

@@ -2097,7 +2097,7 @@ nsDocumentViewer::SetBoundsWithFlags(const nsIntRect& aBounds,
                                      uint32_t aFlags) {
   NS_ENSURE_TRUE(mDocument, NS_ERROR_NOT_AVAILABLE);
 
-  bool boundsChanged = mBounds.IsEqualEdges(aBounds);
+  bool boundsChanged = !mBounds.IsEqualEdges(aBounds);
   mBounds = aBounds;
 
   if (mWindow && !mAttachedToParent) {