merge backout of 153bd6dc88be (bug 553963 pt 3) a=backout

gfx/thebes/gfxUniscribeShaper.cpp

@@ -633,9 +633,10 @@ gfxUniscribeShaper::InitTextRun(gfxContext *aContext,
         }
 
         if (FAILED(rv)) {
+            aTextRun->ResetGlyphRuns();
             // Uniscribe doesn't like this font for some reason.
-            // Returning FALSE will make the gfxGDIFont retry with the
-            // "dumb" GDI one, unless useUniscribeOnly was set.
+            // Returning FALSE will make the gfxGDIFont discard this
+            // shaper and replace it with a "dumb" GDI one.
             result = PR_FALSE;
             break;
         }