Bug 1145007 (part 1) - Test |residentUnique| in test_memoryReporters.xul. r=erahm.

It is the only distinguished amount in nsIMemoryReporterManager that isn't
being tested.

--HG--
extra : rebase_source : a9ba01010a464c6a17e7205212e813c6db4a3d5c

toolkit/components/aboutmemory/tests/test_memoryReporters.xul

@@ -157,6 +157,7 @@
     "vsizeMaxContiguous",
     "resident",
     "residentFast",
+    "residentUnique",
     "heapAllocated",
     "heapOverheadRatio",
     "JSMainRuntimeGCHeap",