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

- Bug 904479 - Added createPromiseWithId() that returns id of resolver r=kanru,nsm (2ac672d882)
- Bug 1166580 - Disable mozHasPendingMessage tests on non-browser platform. r=me (03c689964b)
- Bug 1162281 - Invalid system message handler in an App Manifest can break the entire system. r=fabrice (e192a95f9c)
- Bug 1198988 - Turn off some useless dump() calls r=ferjm (34fc83b236)
- Bug 1164498: Remove |DispatchBluetoothReply|, r=btian (6143335efa)
- Bug 1001757 - Add ability to store core apps outside of profile on desktop b2g; r=fabrice (f6b605e7aa)
- Bug 1155245 - Set the app status correctly for hosted certified apps in developer mode. r=fabrice (131178b80e)
- Bug 1179052 - Add some raptor markers to b2g gecko startup r=gwagner (222256fad8)
- Bug 1163904 - handle -url command line argument. r=fabrice (ee61af1ff9)
- Bug 1167275 - JS error in shell.js handleCmdLine() r=me (32e75c604f)
- Bug 1167197 - Fix GMPProvider on Android r=cpearce Bug 1181209 - Make changes to Gecko needed for b2gdroid to boot. r=fabrice (b35d3a372f)
- Bug 1158544 - Remove FTPChannelChild::mWasOpened and make the base class mWasOpened protected; r=mcmanus (9111e1bc00)
- Bug 1171716 - Part 2: Use NS_ReleaseOnMainThread in nsBaseChannel. r=froydnj (f138124f14)
- partial of Bug 1177175 - Add a UITour target inside the TP panel. (603cc719b3)
- Bug 1175545 - Dont process alt-svc on 421 r=hurley (ad0f2f6e91)
- Bug 1191291 - convert nsHttpChannel::RetargetDeliveryTo warning to log r=michal.novotny (b9c6003df8)
- Bug 1182487 - Don't try to write to HTTP cache entry in nsHttpChannel when entry is open for reading only. r=michal (b36d7014a0)
- Bug 1173069 - Don't accumulate the cache hit telemetry for intercepted channels; r=mayhemer,jdm (aaed79183d)
- Bug 1208755 HttpBaseChannel::ShouldIntercept() should not assume every channel has a LoadInfo. r=ckerschb (d55be94901)
- Bug 1201229 - Return an empty string for a header when an error occurs; r=dragana (256d0462c8)
- Bug 1048048 - add preload content policy types - web platform test updates (r=dveditz) (baa1004dd6)
- Bug 1048048 - add preload content policy types - csp changes (r=dveditz) (17914dadba)
- Bug 1048048 - add preload content policy types for stylesheets (r=cam) (29af13263a)
- Bug 1048048 - add preload content policy types (r=ehsan) (f58a32d51b)
- Bug 1201747 - Don't inspect the subject principal in StorageAllowedForPrincipal. r=mystor (4f2c100882)
- Bug 1176829 - Remove custom elements base element queue. r=smaug (03a520c13d)
- Bug 1176829 follow-up, finish removing unused member to fix bustage. CLOSED TREE (29c6150af8)
- Bug 1179909: Build fix. r=me CLOSED TREE (40e3bdb971)
- Bug 1188932 - Allow the User-Agent header to be explicitly set by requests, r=bkelly, r=jgraham (37aacbd37d)

netwerk/protocol/http/HttpBaseChannel.cpp

@@ -1428,6 +1428,8 @@ NS_IMETHODIMP
 HttpBaseChannel::GetRequestHeader(const nsACString& aHeader,
                                   nsACString& aValue)
 {
+  aValue.Truncate();
+
   // XXX might be better to search the header list directly instead of
   // hitting the http atom hash table.
   nsHttpAtom atom = nsHttp::ResolveAtom(aHeader);
@@ -1503,6 +1505,8 @@ HttpBaseChannel::VisitNonDefaultRequestHeaders(nsIHttpHeaderVisitor *visitor)
 NS_IMETHODIMP
 HttpBaseChannel::GetResponseHeader(const nsACString &header, nsACString &value)
 {
+  value.Truncate();
+
   if (!mResponseHead)
     return NS_ERROR_NOT_AVAILABLE;
 
@@ -2309,7 +2313,7 @@ HttpBaseChannel::ShouldIntercept()
   nsCOMPtr<nsINetworkInterceptController> controller;
   GetCallback(controller);
   bool shouldIntercept = false;
-  if (controller && !mForceNoIntercept) {
+  if (controller && !mForceNoIntercept && mLoadInfo) {
     nsContentPolicyType type = mLoadInfo->InternalContentPolicyType();
     nsresult rv = controller->ShouldPrepareForIntercept(mURI,
                                                         IsNavigation(),