--- a/netwerk/base/RequestContextService.cpp
+++ b/netwerk/base/RequestContextService.cpp
@@ -1,17 +1,17 @@
 /* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 ;*; */
 /* vim: set sw=2 ts=8 et tw=80 : */
 /* This Source Code Form is subject to the terms of the Mozilla Public
  * License, v. 2.0. If a copy of the MPL was not distributed with this
  * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
 
 #include "nsAutoPtr.h"
 #include "nsIObserverService.h"
-#include "nsIUUIDGenerator.h"
+#include "nsIXULRuntime.h"
 #include "nsServiceManagerUtils.h"
 #include "nsThreadUtils.h"
 #include "RequestContextService.h"
 
 #include "mozilla/Atomics.h"
 #include "mozilla/Services.h"
 
 #include "mozilla/net/PSpdyPush.h"
@@ -21,34 +21,32 @@ namespace net {
 
 // nsIRequestContext
 class RequestContext final : public nsIRequestContext
 {
 public:
   NS_DECL_THREADSAFE_ISUPPORTS
   NS_DECL_NSIREQUESTCONTEXT
 
-  explicit RequestContext(const nsID& id);
+  explicit RequestContext(const uint64_t id);
 private:
   virtual ~RequestContext();
 
-  nsID mID;
-  char mCID[NSID_LENGTH];
+  uint64_t mID;
   Atomic<uint32_t>       mBlockingTransactionCount;
   nsAutoPtr<SpdyPushCache> mSpdyCache;
   nsCString mUserAgentOverride;
 };
 
 NS_IMPL_ISUPPORTS(RequestContext, nsIRequestContext)
 
-RequestContext::RequestContext(const nsID& aID)
-  : mBlockingTransactionCount(0)
+RequestContext::RequestContext(const uint64_t aID)
+  : mID(aID)
+  , mBlockingTransactionCount(0)
 {
-  mID = aID;
-  mID.ToProvidedString(mCID);
 }
 
 RequestContext::~RequestContext()
 {
 }
 
 NS_IMETHODIMP
 RequestContext::GetBlockingTransactionCount(uint32_t *aBlockingTransactionCount)
@@ -84,17 +82,17 @@ RequestContext::GetSpdyPushCache(mozilla
 NS_IMETHODIMP
 RequestContext::SetSpdyPushCache(mozilla::net::SpdyPushCache *aSpdyPushCache)
 {
   mSpdyCache = aSpdyPushCache;
   return NS_OK;
 }
 
 NS_IMETHODIMP
-RequestContext::GetID(nsID *outval)
+RequestContext::GetID(uint64_t *outval)
 {
   NS_ENSURE_ARG_POINTER(outval);
   *outval = mID;
   return NS_OK;
 }
 
 NS_IMETHODIMP
 RequestContext::GetUserAgentOverride(nsACString& aUserAgentOverride)
@@ -112,20 +110,24 @@ RequestContext::SetUserAgentOverride(con
 
 
 //nsIRequestContextService
 RequestContextService *RequestContextService::sSelf = nullptr;
 
 NS_IMPL_ISUPPORTS(RequestContextService, nsIRequestContextService, nsIObserver)
 
 RequestContextService::RequestContextService()
+  : mNextRCID(1)
 {
   MOZ_ASSERT(!sSelf, "multiple rcs instances!");
   MOZ_ASSERT(NS_IsMainThread());
   sSelf = this;
+
+  nsCOMPtr<nsIXULRuntime> runtime = do_GetService("@mozilla.org/xre/runtime;1");
+  runtime->GetProcessID(&mRCIDNamespace);
 }
 
 RequestContextService::~RequestContextService()
 {
   MOZ_ASSERT(NS_IsMainThread());
   Shutdown();
   sSelf = nullptr;
 }
@@ -160,17 +162,17 @@ RequestContextService::Create(nsISupport
   RefPtr<RequestContextService> svc = new RequestContextService();
   nsresult rv = svc->Init();
   NS_ENSURE_SUCCESS(rv, rv);
 
   return svc->QueryInterface(aIID, aResult);
 }
 
 NS_IMETHODIMP
-RequestContextService::GetRequestContext(const nsID& rcID, nsIRequestContext **rc)
+RequestContextService::GetRequestContext(const uint64_t rcID, nsIRequestContext **rc)
 {
   MOZ_ASSERT(NS_IsMainThread());
   NS_ENSURE_ARG_POINTER(rc);
   *rc = nullptr;
 
   if (!mTable.Get(rcID, rc)) {
     nsCOMPtr<nsIRequestContext> newSC = new RequestContext(rcID);
     mTable.Put(rcID, newSC);
@@ -182,35 +184,27 @@ RequestContextService::GetRequestContext
 
 NS_IMETHODIMP
 RequestContextService::NewRequestContext(nsIRequestContext **rc)
 {
   MOZ_ASSERT(NS_IsMainThread());
   NS_ENSURE_ARG_POINTER(rc);
   *rc = nullptr;
 
-  nsresult rv;
-  if (!mUUIDGen) {
-    mUUIDGen = do_GetService("@mozilla.org/uuid-generator;1", &rv);
-    NS_ENSURE_SUCCESS(rv, rv);
-  }
-
-  nsID rcID;
-  rv = mUUIDGen->GenerateUUIDInPlace(&rcID);
-  NS_ENSURE_SUCCESS(rv, rv);
+  uint64_t rcID = ((static_cast<uint64_t>(mRCIDNamespace) << 32) & 0xFFFFFFFF00000000LL) | mNextRCID++;
 
   nsCOMPtr<nsIRequestContext> newSC = new RequestContext(rcID);
   mTable.Put(rcID, newSC);
   newSC.swap(*rc);
 
   return NS_OK;
 }
 
 NS_IMETHODIMP
-RequestContextService::RemoveRequestContext(const nsID& rcID)
+RequestContextService::RemoveRequestContext(const uint64_t rcID)
 {
   MOZ_ASSERT(NS_IsMainThread());
   mTable.Remove(rcID);
   return NS_OK;
 }
 
 NS_IMETHODIMP
 RequestContextService::Observe(nsISupports *subject, const char *topic,

--- a/netwerk/base/RequestContextService.h
+++ b/netwerk/base/RequestContextService.h
@@ -7,18 +7,16 @@
 #ifndef mozilla__net__RequestContextService_h
 #define mozilla__net__RequestContextService_h
 
 #include "nsCOMPtr.h"
 #include "nsInterfaceHashtable.h"
 #include "nsIObserver.h"
 #include "nsIRequestContext.h"
 
-class nsIUUIDGenerator;
-
 namespace mozilla {
 namespace net {
 
 class RequestContextService final
   : public nsIRequestContextService
   , public nsIObserver
 {
 public:
@@ -32,16 +30,17 @@ public:
   void Shutdown();
   static nsresult Create(nsISupports *outer, const nsIID& iid, void **result);
 
 private:
   virtual ~RequestContextService();
 
   static RequestContextService *sSelf;
 
-  nsInterfaceHashtable<nsIDHashKey, nsIRequestContext> mTable;
-  nsCOMPtr<nsIUUIDGenerator> mUUIDGen;
+  nsInterfaceHashtable<nsUint64HashKey, nsIRequestContext> mTable;
+  uint32_t mRCIDNamespace;
+  uint32_t mNextRCID;
 };
 
 } // ::mozilla::net
 } // ::mozilla
 
 #endif // mozilla__net__RequestContextService_h

--- a/netwerk/base/nsILoadGroup.idl
+++ b/netwerk/base/nsILoadGroup.idl
@@ -76,17 +76,17 @@ interface nsILoadGroup : nsIRequest
      * Notification callbacks for the load group.
      */
     attribute nsIInterfaceRequestor notificationCallbacks;
 
     /**
      * Context for managing things like js/css connection blocking,
      * and per-tab connection grouping.
      */
-    [noscript] readonly attribute nsID requestContextID;
+    [noscript] readonly attribute unsigned long long requestContextID;
 
     /**
      * The set of load flags that will be added to all new requests added to
      * this group. Any existing requests in the load group are not modified,
      * so it is expected these flags will be added before requests are added
      * to the group - typically via nsIDocShell::defaultLoadFlags on a new
      * docShell.
      * Note that these flags are *not* added to the default request for the

--- a/netwerk/base/nsIRequestContext.idl
+++ b/netwerk/base/nsIRequestContext.idl
@@ -25,17 +25,17 @@ class SpdyPushCache;
  * This used to be known as nsILoadGroupConnectionInfo and nsISchedulingContext.
  */
 [scriptable, uuid(658e3e6e-8633-4b1a-8d66-fa9f72293e63)]
 interface nsIRequestContext : nsISupports
 {
   /**
    * A unique identifier for this request context
    */
-  [noscript] readonly attribute nsID ID;
+  [noscript] readonly attribute unsigned long long ID;
 
   /**
    * Number of active blocking transactions associated with this context
    */
   readonly attribute unsigned long blockingTransactionCount;
 
   /**
    * Increase the number of active blocking transactions associated
@@ -76,20 +76,20 @@ interface nsIRequestContext : nsISupport
  * will get a reference to the same request context you have.
  */
 [uuid(7fcbf4da-d828-4acc-b144-e5435198f727)]
 interface nsIRequestContextService : nsISupports
 {
   /**
    * Get an existing request context from its ID
    */
-  nsIRequestContext getRequestContext(in nsIDRef id);
+  nsIRequestContext getRequestContext(in unsigned long long id);
 
   /**
    * Create a new request context
    */
   nsIRequestContext newRequestContext();
 
   /**
    * Remove an existing request context from its ID
    */
-  void removeRequestContext(in nsIDRef id);
+  void removeRequestContext(in unsigned long long id);
 };

--- a/netwerk/base/nsLoadGroup.cpp
+++ b/netwerk/base/nsLoadGroup.cpp
@@ -122,27 +122,21 @@ nsLoadGroup::nsLoadGroup(nsISupports* ou
 nsLoadGroup::~nsLoadGroup()
 {
     DebugOnly<nsresult> rv = Cancel(NS_BINDING_ABORTED);
     NS_ASSERTION(NS_SUCCEEDED(rv), "Cancel failed");
 
     mDefaultLoadRequest = nullptr;
 
     if (mRequestContext) {
-        nsID rcid;
+        uint64_t rcid;
         mRequestContext->GetID(&rcid);
 
         if (IsNeckoChild() && gNeckoChild) {
-            char rcid_str[NSID_LENGTH];
-            rcid.ToProvidedString(rcid_str);
-
-            nsCString rcid_nscs;
-            rcid_nscs.AssignASCII(rcid_str);
-
-            gNeckoChild->SendRemoveRequestContext(rcid_nscs);
+            gNeckoChild->SendRemoveRequestContext(rcid);
         } else {
             mRequestContextService->RemoveRequestContext(rcid);
         }
     }
 
     LOG(("LOADGROUP [%p]: Destroyed.\n", this));
 }
 
@@ -698,17 +692,17 @@ nsLoadGroup::GetNotificationCallbacks(ns
 NS_IMETHODIMP
 nsLoadGroup::SetNotificationCallbacks(nsIInterfaceRequestor *aCallbacks)
 {
     mCallbacks = aCallbacks;
     return NS_OK;
 }
 
 NS_IMETHODIMP
-nsLoadGroup::GetRequestContextID(nsID *aRCID)
+nsLoadGroup::GetRequestContextID(uint64_t *aRCID)
 {
     if (!mRequestContext) {
         return NS_ERROR_NOT_AVAILABLE;
     }
     return mRequestContext->GetID(aRCID);
 }
 
 ////////////////////////////////////////////////////////////////////////////////

--- a/netwerk/ipc/NeckoChannelParams.ipdlh
+++ b/netwerk/ipc/NeckoChannelParams.ipdlh
@@ -116,17 +116,17 @@ struct HttpChannelOpenArgs
   nsCString                   appCacheClientID;
   bool                        allowSpdy;
   bool                        allowAltSvc;
   bool                        beConservative;
   OptionalLoadInfoArgs        loadInfo;
   OptionalHttpResponseHead    synthesizedResponseHead;
   nsCString                   synthesizedSecurityInfoSerialization;
   uint32_t                    cacheKey;
-  nsCString                   requestContextID;
+  uint64_t                    requestContextID;
   OptionalCorsPreflightArgs   preflightArgs;
   uint32_t                    initialRwin;
   bool                        blockAuthPrompt;
   bool                        suspendAfterSynthesizeResponse;
   bool                        allowStaleCacheContent;
   nsCString                   contentTypeHint;
   nsCString                   channelId;
   uint64_t                    contentWindowId;

--- a/netwerk/ipc/NeckoParent.cpp
+++ b/netwerk/ipc/NeckoParent.cpp
@@ -878,27 +878,25 @@ NeckoParent::RecvPredReset()
     do_GetService("@mozilla.org/network/predictor;1", &rv);
   NS_ENSURE_SUCCESS(rv, IPC_FAIL_NO_REASON(this));
 
   predictor->Reset();
   return IPC_OK();
 }
 
 mozilla::ipc::IPCResult
-NeckoParent::RecvRemoveRequestContext(const nsCString& rcid)
+NeckoParent::RecvRemoveRequestContext(const uint64_t& rcid)
 {
   nsCOMPtr<nsIRequestContextService> rcsvc =
     do_GetService("@mozilla.org/network/request-context-service;1");
   if (!rcsvc) {
     return IPC_OK();
   }
 
-  nsID id;
-  id.Parse(rcid.BeginReading());
-  rcsvc->RemoveRequestContext(id);
+  rcsvc->RemoveRequestContext(rcid);
 
   return IPC_OK();
 }
 
 mozilla::ipc::IPCResult
 NeckoParent::RecvIncreaseThrottlePressure()
 {
   mThrottlers.AppendElement(mozilla::UniquePtr<mozilla::net::Throttler>(new mozilla::net::Throttler));

--- a/netwerk/ipc/NeckoParent.h
+++ b/netwerk/ipc/NeckoParent.h
@@ -218,17 +218,17 @@ protected:
                                                   const bool& hasVerifier) override;
 
   virtual mozilla::ipc::IPCResult RecvPredLearn(const ipc::URIParams& aTargetURI,
                                                 const ipc::OptionalURIParams& aSourceURI,
                                                 const PredictorPredictReason& aReason,
                                                 const OriginAttributes& aOriginAttributes) override;
   virtual mozilla::ipc::IPCResult RecvPredReset() override;
 
-  virtual mozilla::ipc::IPCResult RecvRemoveRequestContext(const nsCString& rcid) override;
+  virtual mozilla::ipc::IPCResult RecvRemoveRequestContext(const uint64_t& rcid) override;
 
   /* Throttler messages */
   virtual mozilla::ipc::IPCResult RecvIncreaseThrottlePressure() override;
   virtual mozilla::ipc::IPCResult RecvDecreaseThrottlePressure() override;
 
   virtual mozilla::ipc::IPCResult
   RecvNotifyCurrentTopLevelOuterContentWindowId(const uint64_t& aWindowId) override;
 private:

--- a/netwerk/ipc/PNecko.ipdl
+++ b/netwerk/ipc/PNecko.ipdl
@@ -109,17 +109,17 @@ parent:
    * These are called from the child with the results of the auth prompt.
    * callbackId is the id that was passed in PBrowser::AsyncAuthPrompt,
    * corresponding to an nsIAuthPromptCallback
    */
   async OnAuthAvailable(uint64_t callbackId, nsString user,
                         nsString password, nsString domain);
   async OnAuthCancelled(uint64_t callbackId, bool userCancel);
 
-  async RemoveRequestContext(nsCString rcid);
+  async RemoveRequestContext(uint64_t rcid);
 
   async PAltDataOutputStream(nsCString type, PHttpChannel channel);
 
   /**
    * Throttling of channels
    */
   async IncreaseThrottlePressure();
   async DecreaseThrottlePressure();

--- a/netwerk/protocol/http/HttpBaseChannel.cpp
+++ b/netwerk/protocol/http/HttpBaseChannel.cpp
@@ -194,16 +194,17 @@ HttpBaseChannel::HttpBaseChannel()
   , mRedirectMode(nsIHttpChannelInternal::REDIRECT_MODE_FOLLOW)
   , mFetchCacheMode(nsIHttpChannelInternal::FETCH_CACHE_MODE_DEFAULT)
   , mOnStartRequestCalled(false)
   , mOnStopRequestCalled(false)
   , mAfterOnStartRequestBegun(false)
   , mTransferSize(0)
   , mDecodedBodySize(0)
   , mEncodedBodySize(0)
+  , mRequestContextID(0)
   , mContentWindowId(0)
   , mTopLevelOuterContentWindowId(0)
   , mRequireCORSPreflight(false)
   , mReportCollector(new ConsoleReportCollector())
   , mAltDataLength(0)
   , mForceMainDocumentChannel(false)
   , mIsTrackingResource(false)
 {
@@ -213,17 +214,16 @@ HttpBaseChannel::HttpBaseChannel()
 #ifdef MOZ_VALGRIND
   // Zero the entire unions so that Valgrind doesn't complain when we send them
   // to another process.
   memset(&mSelfAddr, 0, sizeof(NetAddr));
   memset(&mPeerAddr, 0, sizeof(NetAddr));
 #endif
   mSelfAddr.raw.family = PR_AF_UNSPEC;
   mPeerAddr.raw.family = PR_AF_UNSPEC;
-  mRequestContextID.Clear();
 }
 
 HttpBaseChannel::~HttpBaseChannel()
 {
   LOG(("Destroying HttpBaseChannel @%p\n", this));
 
   // Make sure we don't leak
   CleanRedirectCacheChainIfNecessary();
@@ -2105,25 +2105,25 @@ HttpBaseChannel::RedirectTo(nsIURI *targ
   // This would break the nsIStreamListener contract.
   NS_ENSURE_FALSE(mOnStartRequestCalled, NS_ERROR_NOT_AVAILABLE);
 
   mAPIRedirectToURI = targetURI;
   return NS_OK;
 }
 
 NS_IMETHODIMP
-HttpBaseChannel::GetRequestContextID(nsID *aRCID)
+HttpBaseChannel::GetRequestContextID(uint64_t *aRCID)
 {
   NS_ENSURE_ARG_POINTER(aRCID);
   *aRCID = mRequestContextID;
   return NS_OK;
 }
 
 NS_IMETHODIMP
-HttpBaseChannel::SetRequestContextID(const nsID aRCID)
+HttpBaseChannel::SetRequestContextID(uint64_t aRCID)
 {
   mRequestContextID = aRCID;
   return NS_OK;
 }
 
 NS_IMETHODIMP
 HttpBaseChannel::GetIsMainDocumentChannel(bool* aValue)
 {
@@ -3806,19 +3806,17 @@ HttpBaseChannel::GetThrottleQueue(nsIInp
   return NS_OK;
 }
 
 //------------------------------------------------------------------------------
 
 bool
 HttpBaseChannel::EnsureRequestContextID()
 {
-    nsID nullID;
-    nullID.Clear();
-    if (!mRequestContextID.Equals(nullID)) {
+    if (mRequestContextID) {
         // Already have a request context ID, no need to do the rest of this work
         return true;
     }
 
     // Find the loadgroup at the end of the chain in order
     // to make sure all channels derived from the load group
     // use the same connection scope.
     nsCOMPtr<nsILoadGroupChild> childLoadGroup = do_QueryInterface(mLoadGroup);

--- a/netwerk/protocol/http/HttpBaseChannel.h
+++ b/netwerk/protocol/http/HttpBaseChannel.h
@@ -188,21 +188,21 @@ public:
   NS_IMETHOD SetRedirectionLimit(uint32_t value) override;
   NS_IMETHOD IsNoStoreResponse(bool *value) override;
   NS_IMETHOD IsNoCacheResponse(bool *value) override;
   NS_IMETHOD IsPrivateResponse(bool *value) override;
   NS_IMETHOD GetResponseStatus(uint32_t *aValue) override;
   NS_IMETHOD GetResponseStatusText(nsACString& aValue) override;
   NS_IMETHOD GetRequestSucceeded(bool *aValue) override;
   NS_IMETHOD RedirectTo(nsIURI *newURI) override;
-  NS_IMETHOD GetRequestContextID(nsID *aRCID) override;
+  NS_IMETHOD GetRequestContextID(uint64_t *aRCID) override;
   NS_IMETHOD GetTransferSize(uint64_t *aTransferSize) override;
   NS_IMETHOD GetDecodedBodySize(uint64_t *aDecodedBodySize) override;
   NS_IMETHOD GetEncodedBodySize(uint64_t *aEncodedBodySize) override;
-  NS_IMETHOD SetRequestContextID(const nsID aRCID) override;
+  NS_IMETHOD SetRequestContextID(uint64_t aRCID) override;
   NS_IMETHOD GetIsMainDocumentChannel(bool* aValue) override;
   NS_IMETHOD SetIsMainDocumentChannel(bool aValue) override;
   NS_IMETHOD GetProtocolVersion(nsACString & aProtocolVersion) override;
   NS_IMETHOD GetChannelId(nsACString& aChannelId) override;
   NS_IMETHOD SetChannelId(const nsACString& aChannelId) override;
   NS_IMETHOD GetTopLevelContentWindowId(uint64_t *aContentWindowId) override;
   NS_IMETHOD SetTopLevelContentWindowId(uint64_t aContentWindowId) override;
   NS_IMETHOD GetIsTrackingResource(bool* aIsTrackingResource) override;
@@ -581,17 +581,17 @@ protected:
 
   uint64_t mTransferSize;
   uint64_t mDecodedBodySize;
   uint64_t mEncodedBodySize;
 
   // The network interface id that's associated with this channel.
   nsCString mNetworkInterfaceId;
 
-  nsID mRequestContextID;
+  uint64_t mRequestContextID;
   bool EnsureRequestContextID();
 
   // ID of the top-level document's inner window this channel is being
   // originated from.
   uint64_t mContentWindowId;
 
   uint64_t mTopLevelOuterContentWindowId;
   void EnsureTopLevelOuterContentWindowId();

--- a/netwerk/protocol/http/HttpChannelChild.cpp
+++ b/netwerk/protocol/http/HttpChannelChild.cpp
@@ -2238,19 +2238,17 @@ HttpChannelChild::ContinueAsyncOpen()
   openArgs.allowStaleCacheContent() = mAllowStaleCacheContent;
 
   openArgs.contentTypeHint() = mContentTypeHint;
 
   nsresult rv = mozilla::ipc::LoadInfoToLoadInfoArgs(mLoadInfo, &openArgs.loadInfo());
   NS_ENSURE_SUCCESS(rv, rv);
 
   EnsureRequestContextID();
-  char rcid[NSID_LENGTH];
-  mRequestContextID.ToProvidedString(rcid);
-  openArgs.requestContextID().AssignASCII(rcid);
+  openArgs.requestContextID() = mRequestContextID;
 
   char chid[NSID_LENGTH];
   mChannelId.ToProvidedString(chid);
   openArgs.channelId().AssignASCII(chid);
 
   openArgs.contentWindowId() = contentWindowId;
   openArgs.topLevelOuterContentWindowId() = mTopLevelOuterContentWindowId;
 

--- a/netwerk/protocol/http/HttpChannelParent.cpp
+++ b/netwerk/protocol/http/HttpChannelParent.cpp
@@ -316,17 +316,17 @@ HttpChannelParent::DoAsyncOpen(  const U
                                  const nsCString&           appCacheClientID,
                                  const bool&                allowSpdy,
                                  const bool&                allowAltSvc,
                                  const bool&                beConservative,
                                  const OptionalLoadInfoArgs& aLoadInfoArgs,
                                  const OptionalHttpResponseHead& aSynthesizedResponseHead,
                                  const nsCString&           aSecurityInfoSerialization,
                                  const uint32_t&            aCacheKey,
-                                 const nsCString&           aRequestContextID,
+                                 const uint64_t&            aRequestContextID,
                                  const OptionalCorsPreflightArgs& aCorsPreflightArgs,
                                  const uint32_t&            aInitialRwin,
                                  const bool&                aBlockAuthPrompt,
                                  const bool&                aSuspendAfterSynthesizeResponse,
                                  const bool&                aAllowStaleCacheContent,
                                  const nsCString&           aContentTypeHint,
                                  const nsCString&           aChannelId,
                                  const uint64_t&            aContentWindowId,
@@ -574,19 +574,17 @@ HttpChannelParent::DoAsyncOpen(  const U
       // This works because we've already called SetNotificationCallbacks and
       // done mPBOverride logic by this point.
       chooseAppCache = NS_ShouldCheckAppCache(principal, NS_UsePrivateBrowsing(mChannel));
 
       appCacheChan->SetChooseApplicationCache(chooseAppCache);
     }
   }
 
-  nsID requestContextID;
-  requestContextID.Parse(aRequestContextID.BeginReading());
-  mChannel->SetRequestContextID(requestContextID);
+  mChannel->SetRequestContextID(aRequestContextID);
 
   mSuspendAfterSynthesizeResponse = aSuspendAfterSynthesizeResponse;
 
   if (!delayAsyncOpen) {
     InvokeAsyncOpen(NS_OK);
   }
 
   return true;

--- a/netwerk/protocol/http/HttpChannelParent.h
+++ b/netwerk/protocol/http/HttpChannelParent.h
@@ -134,17 +134,17 @@ protected:
               const nsCString&           appCacheClientID,
               const bool&                allowSpdy,
               const bool&                allowAltSvc,
               const bool&                beConservative,
               const OptionalLoadInfoArgs& aLoadInfoArgs,
               const OptionalHttpResponseHead& aSynthesizedResponseHead,
               const nsCString&           aSecurityInfoSerialization,
               const uint32_t&            aCacheKey,
-              const nsCString&           aRequestContextID,
+              const uint64_t&            aRequestContextID,
               const OptionalCorsPreflightArgs& aCorsPreflightArgs,
               const uint32_t&            aInitialRwin,
               const bool&                aBlockAuthPrompt,
               const bool&                aSuspendAfterSynthesizeResponse,
               const bool&                aAllowStaleCacheContent,
               const nsCString&           aContentTypeHint,
               const nsCString&           aChannelId,
               const uint64_t&            aContentWindowId,

--- a/netwerk/protocol/http/NullHttpChannel.cpp
+++ b/netwerk/protocol/http/NullHttpChannel.cpp
@@ -272,23 +272,23 @@ NullHttpChannel::IsPrivateResponse(bool 
 
 NS_IMETHODIMP
 NullHttpChannel::RedirectTo(nsIURI *aNewURI)
 {
   return NS_ERROR_NOT_IMPLEMENTED;
 }
 
 NS_IMETHODIMP
-NullHttpChannel::GetRequestContextID(nsID *_retval)
+NullHttpChannel::GetRequestContextID(uint64_t *_retval)
 {
   return NS_ERROR_NOT_IMPLEMENTED;
 }
 
 NS_IMETHODIMP
-NullHttpChannel::SetRequestContextID(const nsID rcID)
+NullHttpChannel::SetRequestContextID(uint64_t rcID)
 {
   return NS_ERROR_NOT_IMPLEMENTED;
 }
 
 NS_IMETHODIMP
 NullHttpChannel::GetProtocolVersion(nsACString& aProtocolVersion)
 {
   return NS_ERROR_NOT_IMPLEMENTED;

--- a/netwerk/protocol/http/nsIHttpChannel.idl
+++ b/netwerk/protocol/http/nsIHttpChannel.idl
@@ -442,17 +442,17 @@ interface nsIHttpChannel : nsIChannel
      * @throws NS_ERROR_NOT_AVAILABLE if called after the channel has already
      *         started to deliver the content to its listener.
      */
     [must_use] void redirectTo(in nsIURI aTargetURI);
 
     /**
      * Identifies the request context for this load.
      */
-    [noscript, must_use] attribute nsID requestContextID;
+    [noscript, must_use] attribute uint64_t requestContextID;
 
     /**
      * Unique ID of the channel, shared between parent and child. Needed if
      * the channel activity needs to be monitored across process boundaries,
      * like in devtools net monitor. See bug 1274556.
      */
     [must_use] attribute ACString channelId;
 

--- a/netwerk/protocol/viewsource/nsViewSourceChannel.cpp
+++ b/netwerk/protocol/viewsource/nsViewSourceChannel.cpp
@@ -983,24 +983,24 @@ nsViewSourceChannel::IsPrivateResponse(b
 NS_IMETHODIMP
 nsViewSourceChannel::RedirectTo(nsIURI *uri)
 {
     return !mHttpChannel ? NS_ERROR_NULL_POINTER :
         mHttpChannel->RedirectTo(uri);
 }
 
 NS_IMETHODIMP
-nsViewSourceChannel::GetRequestContextID(nsID *_retval)
+nsViewSourceChannel::GetRequestContextID(uint64_t *_retval)
 {
     return !mHttpChannel ? NS_ERROR_NULL_POINTER :
         mHttpChannel->GetRequestContextID(_retval);
 }
 
 NS_IMETHODIMP
-nsViewSourceChannel::SetRequestContextID(const nsID rcid)
+nsViewSourceChannel::SetRequestContextID(uint64_t rcid)
 {
     return !mHttpChannel ? NS_ERROR_NULL_POINTER :
         mHttpChannel->SetRequestContextID(rcid);
 }
 
 NS_IMETHODIMP
 nsViewSourceChannel::GetIsMainDocumentChannel(bool* aValue)
 {