Bug 958726 - Perform shrinking GC if nsJSContext::GarbageCollectNow is called with aShrinking == ShrinkingGC. r=billm

--HG--
extra : rebase_source : b590c474fc195e2118de19f4ce9747bb4407d0f0

dom/base/nsJSEnvironment.cpp

@@ -1926,7 +1926,10 @@ nsJSContext::GarbageCollectNow(JS::gcreason::Reason aReason,
 
   JS::PrepareForFullGC(sRuntime);
   if (aIncremental == IncrementalGC) {
+    MOZ_ASSERT(aShrinking == NonShrinkingGC);
     JS::IncrementalGC(sRuntime, aReason, aSliceMillis);
+  } else if (aShrinking == ShrinkingGC) {
+    JS::ShrinkingGC(sRuntime, aReason);
   } else {
     JS::GCForReason(sRuntime, aReason);
   }