Restore the ability to tab to links in an imagemap. Bug 304467, r+sr=roc, a=asa

git-svn-id: svn://10.0.0.236/branches/MOZILLA_1_8_BRANCH@178853 18797224-902f-48f8-a5cc-f745e15eee43

mozilla/layout/generic/nsImageMap.cpp

@@ -901,6 +901,8 @@ nsImageMap::AddArea(nsIContent* aArea)
   }
 
   mPresShell->FrameManager()->SetPrimaryFrameFor(aArea, mImageFrame);
+  aArea->SetMayHaveFrame(PR_TRUE);
+  NS_ASSERTION(aArea->MayHaveFrame(), "SetMayHaveFrame failed?");
 
   area->ParseCoords(coords);
   mAreas.AppendElement(area);