merge mozilla-inbound to mozilla-central. r=merge a=merge

MozReview-Commit-ID: IC9EbX0bomM

layout/generic/nsGfxScrollFrame.cpp

@@ -2714,6 +2714,9 @@ ScrollFrameHelper::ScheduleSyntheticMouseMove()
     if (!mScrollActivityTimer) {
       return;
     }
+
+    mScrollActivityTimer->SetTarget(
+      mOuter->PresContext()->Document()->EventTargetFor(TaskCategory::Other));
   }
 
   mScrollActivityTimer->InitWithNamedFuncCallback(

xpcom/base/CycleCollectedJSRuntime.cpp

@@ -1426,7 +1426,7 @@ CycleCollectedJSRuntime::FinalizeDeferredThings(CycleCollectedJSContext::Deferre
   MOZ_ASSERT(mDeferredFinalizerTable.Count() == 0);
 
   if (aType == CycleCollectedJSContext::FinalizeIncrementally) {
-    NS_DispatchToCurrentThread(mFinalizeRunnable);
+    NS_IdleDispatchToCurrentThread(do_AddRef(mFinalizeRunnable), 2500);
   } else {
     mFinalizeRunnable->ReleaseNow(false);
     MOZ_ASSERT(!mFinalizeRunnable);