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

- Bug 1240094 - nsDocShell should initialize mUserContextId to nsIScriptSecurityManager::DEFAULT_USER_CONTEXT_ID, r=smaug (a3a8358561)
- Bug 1142768 - Return the original document URI from ServiceWorkerClient.url; r=bkelly (17892631ab)
- Bug 1233613 - Make RegisterFrameCaptureListener fallible. r=mt (0a68d5f4ac)
- Bug 1233613 - Locate parent document before getting presentation shell for canvas capture. r=mt (47a285deab)
- Bug 866513 - Non-empty MediaStreamTrack labels. r=jib (1b1f364811)
- Bug 1170958 - Don't create owned MediaStreamTracks in MetadataLoaded. r=roc (3f031298fb)
- fix misspatch of Bug 1131802 part 2 (3a1e0d2799)
- trivial fixes (bffbd65448)
- Bug 1218454 - part 2a - fix bootlegging of nsContentUtils.h includes from nsILoadContext.h; r=bz (a587b686cd)
- bit of Bug 1223078 - Release WrappedJS eagerly (1fcb1a490b)
- Bug 1245767 followup - Throw an error when gczeal argument is out of range. r=jonco on IRC (32de34e6b7)
- Bug 1241934 - Remove the unused validategc API; r=jonco (a80436895b)
- Bug 961323 - Add a method for finding shortest retaining paths of `JS::ubi::Node` heap graphs; r=jimb (b2d3735d7d)
- Bug 1240090 - Make owned copies of filenames in JS::ubi::ByFilename. r=jimb (049ab3c6ed)
- Bug 1247412 - Add a reverse method to mozilla::Vector; r=Waldo (ad417ff38b)
- Bug 1247413 - Give JS::ubi::BreadthFirst handlers a non-const reference; r=jimb (9baadfa50e)
- bit of Bug 1246061 (51b6ef81dc)
- Bug 1243198 - Use rvalue references for JS::ubi::ByFilename constructor; r=jimb (5b1dab61a5)
- Bug 1216001 part 1 - Optimize nsRange::IsNodeSelected. r=bz (39aad5f0d4)
- Bug 1216001 part 2 - Optimize nsRange::ExcludeNonSelectableNodes by counting ignorable whitespace text nodes next to an unselectable node as unselectable too. r=bz (c6589b508e)
- Bug 1216001 part 3 - Cache the result of IsSelected() for the duration of painting. r=bz (aa5c000b4c)
- Bug 1188364 - Supress GC while transplanting to prevent compacting GC observing intermediate state r=terrence (6963b58989)
- Bug 1246318 - Make the proxy enumerate trap non-standard. r=efaust (f34d0a7c2a)
- Bug 1254293. Fix dom::GetArrayIndexFromId to actually follow the spec for large indices (i.e. ones that don't fit in in int32_t). r=peterv (b71cffbbbd)
- Bug 1256688 - Change BPH::has to follow [[HasProperty]] for ordinary objects. r=jorendorff (39b8de1a3d)

docshell/base/nsDocShell.cpp

@@ -804,6 +804,7 @@ nsDocShell::nsDocShell()
   , mBlankTiming(false)
   , mFrameType(eFrameTypeRegular)
   , mOwnOrContainingAppId(nsIScriptSecurityManager::UNKNOWN_APP_ID)
+  , mUserContextId(nsIScriptSecurityManager::DEFAULT_USER_CONTEXT_ID)
   , mParentCharsetSource(0)
   , mJSRunToCompletionDepth(0)
 {