import changes from `dev' branch of rmottola/Arctic-Fox:

- Bug 1170958 - Feed a SourceMediaStream-backed dom stream instead of a raw SourceMediaStream in MediaManager. r=jesup (8670ff2711)
- Bug 1103188 - Remove identical override nsDOMUserMediaStream::Stop(). r=jib (54831f9b18)
- Bug 1103188 - Deprecate DOMMediaStream::Stop(). r=jib (36112afe82)
- Bug 1186813 - Replace nsBaseHashtable::EnumerateRead() calls in dom/media/ with iterators r=cpearce (cd0c4a34e8)
- Bug 1190337 - Log GPS status and SVs status if the 'gDebug_isLoggingEnabled' is true. r=garvank (c269f6f31d)
- Bug 1154435 - [Stumbler] FxOS Geo Stumbling for Mozilla Location Service. r=jdm (1a86f4dda5)
- Bug 1199395 - FxOS Stumbling gzip the stumbles to store more data. r=jdm (4d108665d9)
- Bug 1175860 - Add some documentation to UploadLastDir to make its workings clearer. r=baku (cdac9a7849)
- Bug 1210517 - Create nsVariant directly rather than via do_CreateInstance(). r=froydnj (df420cba8e)
- Bug 953265: make getUserMedia fake audio tones configurable in frequency via pref r=jib (67793ee005)
- Bug 1166293 - Use AsyncShutdown API to shut down media thread in non-e10s. r= jesup (1245d20b7e)
- Bug 1103188 - MediaStream WebIDL update with addTrack/removeTrack. r=smaug,jib (697791fd6f)
- Bug 1103188 - MediaStream::AddTrack/RemoveTrack implementation. r=roc (c8b02beb45)
- Bug 1170958 - Improve logging of MediaStreams and playback. r=roc (5fcb40437e)
- Bug 1170958 - Add DOMMediaStream::OwnedStreamListener. r=roc (afff077f93)
- Bug 1103188 - Break out MediaTrackListListener to an interface. r=roc (298b665f27)
- Bug 1198435 - Call RemoveMediaElementFromURITable before modifying mLoadingSrc, so that a future LookupMediaElementURITable won't access this element anymore. r=rillian (f2805c8dba)
- Bug 1141875 - Add flag to init gl_Position. - r=kamidphish (eeb333c02b)
- Bug 1128044 - Enforce packing restrictions for varyings. - r=kamidphish (17b9596a3d)
- Bug 1128044 - Only pack varyings that have static use in both shaders. - r=warnings-as-errors (f41708642a)
- Bug 1128044 - Use nsTArray since android doesn't support std::vector::data(). - r=bustage (be88a80844)
- Bug 1128044 - nsTArray::AppendElement doesn't accept init lists. - r=bustage (cdeafa867b)
- bit of Bug 1019209 - Allow GL initialization without Android bridge (3dba5dffa2)
- some reporter (3049ad6f6d)
- Bug 1206030 - Remove nsIDOMHTMLCanvasElement::MozFetchAsStream() f=Ms2ger r=jst (95e773b79f)
- Bug 1187174 - Use 'webgl2' not 'experimental-webgl2'. - r=kamidphish (a6c21752fc)
- Bug 1190777 - Add null checks to prevent bad dereferences. r=kamidphish (f67f0125ce)
- Bug 709490 - Part 1: Let ImageBridge transfer CanvasClient async. r=nical (a46ac7e71c)
- Bug 1150762 - Add pref for activating all ANGLE options. - r=kamidphish (6ab4d39827)
- Bug 1195401 - Use gfxPrefs (threadsafe) rather than crashing on debug builds for off-main-thread pref access. r=snorp (0d29cea59c)
- Bug 709490 - Part 2: Introduce OffscreenCanvas and let WebGL context work on workers. r=nical, r=jgilbert, r=jrmuizel, sr=ehsan (842aaa8328)
- Bug 709490 - Part 3: Transfer OffscreenCanvas from mainthread to workers. r=baku, r=sfink (91c24b0e08)
- Bug 709490 - Part 4: Mochitests for offscreencanvas. r=baku, r=jgilbert (4c439fd376)
- Bug 1173544 - Add tests for Canvas CSS/SVG Filters. r=mstange (04c01f1c11)
- fix (9c7ab9d870)
- Bug 709490 - Part 5: Add interfaces test. r=ehsan (2993581c89)
- Bug 709490 - Part 6: Add frame ID to CanvasClient so compositor could update frame correctly. r=roc (3e6554af1e)
- Bug 709490 - Part 7: If layer is not available, fallback to BasicCanvasLayer. r=roc (c0c0d04468)
- Bug 709490 - Part 8: Copy to a temp texture when readback from IOSurface. r=jgilbert (d1a4879a39)
- Bug 709490 - Part 9: Readback without blocking main thread. r=jgilbert (2430c6e2a5)
- Bug 709490 - Part 10: Using mechanism in RuntimeService to get pref in worker thread instead of gfxPref. r=baku (85d6dc2744)
- Bug 709490 - Part 11: Diabled test_offscreencanvas_many.html on gonk, android, windows and linux. r=jgilbert (5cd8f28063)
- Bug 1212663 - Use doxygen style comments in jsapi, r=Waldo (0e67283edf)
- Bug 1000922 - Use nsMainThreadPtrHandle instead of already_AddRefed and forget for callbacks in NativeOSFileInternals.cpp r=jdm (4a128db7a6)
- Bug 1169740 - Implement a TDZ-like behavior for |this| in derived class constructors. (r=jandem, r=jorendorff, inputs on nit resoulution from Waldo) (6d7df317e3)
- Bug 1211949 - check for allocation failure. r=nbp (94b8aac5e3)
- Bug 1209497 - OOM-crash if a consistent object table is impossible. r=jandem (e8ded0c3cb)
- Bug 1141863 - Part 1: Make |this| object creation account for new.target. (r=jandem, r=jorendorff) (9b4ec25d47)
- Bug 1141863 - Part 2: Implement ES6 SuperCall. (r=jandem, r=jorendorff) (1bbd2ba712)
- Bug 1141863 - Followup: Clean up proxy get traps to handle new |this| creation semantics. (rs=Waldo) CLOSED TREE (e7cd48b43c)
- Bug 1141863 - Last followup fix for a couple jstest failures. r=orange in a CLOSED TREE (8a9cff881a)
- Bug 1141863 - Followfollowfollowup: Remove redundant assert causing rooting hazards. (r=Waldo over IRC) CLOSED TREE (338b64ca87)
- Bug 1141863 - Tests. (r=jorendorff) (3957511169)
- Bug 1105463 - Implement default constructors for ES6 class definitions. (r=jorendorff) (8ead7f33a5)
- Bug 1105463 - Follow up: Fix erroneous syntax test. (r=theSheriffMadeMeDoIt) (425e678cf2)
- Bug 1212794 - Remove decompile-body functionality. r=till (9b87e5c0e4)
- Bug 1214970 - Don't emit nullptr atoms for class expressions with default constructors. (r=Waldo) (80ae19d6dc)
- Bug 1215744 - Unnamed class expressions shouldn't get a name property. (r=arai) (0ce0a96be4)
- Bug 1208747 - Move most of Stopwatch-related code to XPCOM-land (JSAPI-level);r=jandem (e28fa2f859)
- Bug 1184486 - Let PerformanceStats.jsm play nicer with process-per-tab. r=mconley (f0cf0d0eae)
- Bug 1198167 - nsPerformanceStatsService should wait for profile-before-change, not profile-before-shutdown. r=yoric (5ba3c98109)
- Bug 1199603 - Don't wait for shutdown to update nsPerformanceStats Telemetry. r=Mossop (110813977b)
- Bug 1205154 - Use channel->Open2() in js/xpconnect/src/XPCJSRuntime.cpp (r=sicking) (8efd629889)
- Bug 1208747 - Move most of Stopwatch-related code to XPCOM-land (XPCOM-level + XPConnect-level);r=froydnj (a1b1e83549)
- with some fixes

dom/html/HTMLInputElement.cpp

@@ -63,6 +63,7 @@
 #include "nsReadableUtils.h"
 #include "nsUnicharUtils.h"
 #include "nsLayoutUtils.h"
+#include "nsVariant.h"
 
 #include "nsIDOMMutationEvent.h"
 #include "mozilla/ContentEvents.h"
@@ -807,11 +808,12 @@ UploadLastDir::StoreLastUsedDirectory(nsIDocument* aDoc, nsIFile* aDir)
   aDir->GetPath(unicodePath);
   if (unicodePath.IsEmpty()) // nothing to do
     return NS_OK;
-  nsCOMPtr<nsIWritableVariant> prefValue = do_CreateInstance(NS_VARIANT_CONTRACTID);
-  if (!prefValue)
-    return NS_ERROR_OUT_OF_MEMORY;
+  RefPtr<nsVariant> prefValue = new nsVariant();
   prefValue->SetAsAString(unicodePath);
 
+  // Use the document's current load context to ensure that the content pref
+  // service doesn't persistently store this directory for this domain if the
+  // user is using private browsing:
   nsCOMPtr<nsILoadContext> loadContext = aDoc->GetLoadContext();
   return contentPrefService->Set(spec, CPS_PREF_NAME, prefValue, loadContext, nullptr);
 }