--- a/netwerk/protocol/http/HttpBaseChannel.cpp
+++ b/netwerk/protocol/http/HttpBaseChannel.cpp
@@ -176,17 +176,16 @@ HttpBaseChannel::HttpBaseChannel()
   , mAllowAltSvc(true)
   , mBeConservative(false)
   , mResponseTimeoutEnabled(true)
   , mAllRedirectsSameOrigin(true)
   , mAllRedirectsPassTimingAllowCheck(true)
   , mResponseCouldBeSynthesized(false)
   , mBlockAuthPrompt(false)
   , mAllowStaleCacheContent(false)
-  , mHasListenerForTraceableChannel(false)
   , mSuspendCount(0)
   , mInitialRwin(0)
   , mProxyResolveFlags(0)
   , mContentDispositionHint(UINT32_MAX)
   , mHttpHandler(gHttpHandler)
   , mReferrerPolicy(NS_GetDefaultReferrerPolicy())
   , mRedirectCount(0)
   , mForcePending(false)
@@ -2936,17 +2935,16 @@ HttpBaseChannel::SetNewListener(nsIStrea
 
   NS_ENSURE_STATE(mListener);
   NS_ENSURE_ARG_POINTER(aListener);
 
   nsCOMPtr<nsIStreamListener> wrapper = new nsStreamListenerWrapper(mListener);
 
   wrapper.forget(_retval);
   mListener = aListener;
-  mHasListenerForTraceableChannel = true;
   return NS_OK;
 }
 
 //-----------------------------------------------------------------------------
 // HttpBaseChannel helpers
 //-----------------------------------------------------------------------------
 
 void

--- a/netwerk/protocol/http/HttpBaseChannel.h
+++ b/netwerk/protocol/http/HttpBaseChannel.h
@@ -343,18 +343,16 @@ public: /* Necko internal use only... */
     // mListenerContext.
     nsresult DoApplyContentConversions(nsIStreamListener *aNextListener,
                                        nsIStreamListener **aNewNextListener);
 
     // Callback on main thread when NS_AsyncCopy() is finished populating
     // the new mUploadStream.
     void EnsureUploadStreamIsCloneableComplete(nsresult aStatus);
 
-    bool HasListenerForTraceableChannel() { return mHasListenerForTraceableChannel; }
-
     void SetIsTrackingResource()
     {
       mIsTrackingResource = true;
     }
 
 protected:
   // Handle notifying listener, removing from loadgroup if request failed.
   void     DoNotifyListener();
@@ -512,18 +510,16 @@ protected:
   uint32_t                          mResponseCouldBeSynthesized : 1;
 
   uint32_t                          mBlockAuthPrompt : 1;
 
   // If true, we behave as if the LOAD_FROM_CACHE flag has been set.
   // Used to enforce that flag's behavior but not expose it externally.
   uint32_t                          mAllowStaleCacheContent : 1;
 
-  uint32_t                          mHasListenerForTraceableChannel : 1;
-
   // Current suspension depth for this channel object
   uint32_t                          mSuspendCount;
 
   // Per channel transport window override (0 means no override)
   uint32_t                          mInitialRwin;
 
   nsAutoPtr<nsTArray<nsCString> >   mRedirectedCachekeys;
 

--- a/netwerk/protocol/http/HttpChannelChild.cpp
+++ b/netwerk/protocol/http/HttpChannelChild.cpp
@@ -175,17 +175,16 @@ HttpChannelChild::HttpChannelChild()
   , mSuspendSent(false)
   , mSynthesizedResponse(false)
   , mShouldInterceptSubsequentRedirect(false)
   , mRedirectingForSubsequentSynthesizedResponse(false)
   , mPostRedirectChannelShouldIntercept(false)
   , mPostRedirectChannelShouldUpgrade(false)
   , mShouldParentIntercept(false)
   , mSuspendParentAfterSynthesizeResponse(false)
-  , mContentDecodingWillBeCalledOnParent(false)
 {
   LOG(("Creating HttpChannelChild @%p\n", this));
 
   mChannelCreationTime = PR_Now();
   mChannelCreationTimestamp = TimeStamp::Now();
   mAsyncOpenTime = TimeStamp::Now();
   mEventQ = new ChannelEventQueue(static_cast<nsIHttpChannel*>(this));
 }
@@ -378,32 +377,29 @@ HttpChannelChild::RecvOnStartRequest(con
                                      const bool& cacheEntryAvailable,
                                      const uint32_t& cacheExpirationTime,
                                      const nsCString& cachedCharset,
                                      const nsCString& securityInfoSerialization,
                                      const NetAddr& selfAddr,
                                      const NetAddr& peerAddr,
                                      const int16_t& redirectCount,
                                      const uint32_t& cacheKey,
-                                     const nsCString& altDataType,
-                                     const bool& contentDecodingWillBeCalledOnParent)
+                                     const nsCString& altDataType)
 {
   LOG(("HttpChannelChild::RecvOnStartRequest [this=%p]\n", this));
   // mFlushedForDiversion and mDivertingToParent should NEVER be set at this
   // stage, as they are set in the listener's OnStartRequest.
   MOZ_RELEASE_ASSERT(!mFlushedForDiversion,
     "mFlushedForDiversion should be unset before OnStartRequest!");
   MOZ_RELEASE_ASSERT(!mDivertingToParent,
     "mDivertingToParent should be unset before OnStartRequest!");
 
 
   mRedirectCount = redirectCount;
 
-  mContentDecodingWillBeCalledOnParent = contentDecodingWillBeCalledOnParent;
-
   mEventQ->RunOrEnqueue(new StartRequestEvent(this, channelStatus, responseHead,
                                               useResponseHead, requestHeaders,
                                               isFromCache, cacheEntryAvailable,
                                               cacheExpirationTime,
                                               cachedCharset,
                                               securityInfoSerialization,
                                               selfAddr, peerAddr, cacheKey,
                                               altDataType));
@@ -554,36 +550,16 @@ HttpChannelChild::DoOnStartRequest(nsIRe
     return;
   }
   nsresult rv = mListener->OnStartRequest(aRequest, aContext);
   if (NS_FAILED(rv)) {
     Cancel(rv);
     return;
   }
 
-  if (mContentDecodingWillBeCalledOnParent) {
-    // Whether we need to do a data conversion or not is decided during
-    // OnStartRequest call. nsURILoader and nsExternalHelperAppService are
-    // making this decision on the child.
-    // If the parent channel has a listener for the TracableChannel interface,
-    // we need to convert the data before giving it to the listent, e.g. we
-    // need to convert the data on the parent.
-    //
-    // After calling OnStartRequest check if we need to do a data conversion or
-    // not and inform the parent about the decision.
-    bool doContentConversion;
-    GetApplyConversion(&doContentConversion);
-    SetApplyConversion(false);
-    SendApplyConversion(doContentConversion);
-    mContentDecodingWillBeCalledOnParent = false;
-    LOG(("HttpChannelChild::DoOnStartRequest [this=%p] doing content decoding"
-         " on the parent; doContentEncoding=%d \n",
-         this, doContentConversion));
-  }
-
   if (mDivertingToParent) {
     mListener = nullptr;
     mListenerContext = nullptr;
     mCompressListener = nullptr;
     if (mLoadGroup) {
       mLoadGroup->RemoveRequest(this, nullptr, mStatus);
     }
 
@@ -1849,22 +1825,16 @@ HttpChannelChild::OnRedirectVerifyCallba
 //-----------------------------------------------------------------------------
 
 NS_IMETHODIMP
 HttpChannelChild::Cancel(nsresult status)
 {
   LOG(("HttpChannelChild::Cancel [this=%p]\n", this));
   MOZ_ASSERT(NS_IsMainThread());
 
-  if (mContentDecodingWillBeCalledOnParent) {
-    LOG(("HttpChannelChild::Cancel call SendApplyConversion [this=%p]\n", this));
-    SendApplyConversion(false);
-    mContentDecodingWillBeCalledOnParent = false;
-  }
-
   if (!mCanceled) {
     // If this cancel occurs before nsHttpChannel has been set up, AsyncOpen
     // is responsible for cleaning up.
     mCanceled = true;
     mStatus = status;
     if (RemoteChannelExists())
       SendCancel(status);
     if (mSynthesizedResponsePump) {
@@ -2792,22 +2762,16 @@ HttpChannelChild::DivertToParent(Channel
   HttpChannelDiverterArgs args;
   args.mChannelChild() = this;
   args.mApplyConversion() = mApplyConversion;
 
   PChannelDiverterChild* diverter =
     gNeckoChild->SendPChannelDiverterConstructor(args);
   MOZ_RELEASE_ASSERT(diverter);
 
-  // When a request is diverted to the parent, OnStartRequest of all listeners
-  // are called on the parent (and of course the end decision whether data
-  // should be converted or not is made on the parent), therefore just clear
-  // mContentDecodingWillBeCalledOnParent and do not send SendApplyConversion.
-  mContentDecodingWillBeCalledOnParent = false;
-
   *aChild = static_cast<ChannelDiverterChild*>(diverter);
 
   return NS_OK;
 }
 
 NS_IMETHODIMP
 HttpChannelChild::UnknownDecoderInvolvedKeepData()
 {

--- a/netwerk/protocol/http/HttpChannelChild.h
+++ b/netwerk/protocol/http/HttpChannelChild.h
@@ -118,18 +118,17 @@ protected:
                                              const bool& cacheEntryAvailable,
                                              const uint32_t& cacheExpirationTime,
                                              const nsCString& cachedCharset,
                                              const nsCString& securityInfoSerialization,
                                              const NetAddr& selfAddr,
                                              const NetAddr& peerAddr,
                                              const int16_t& redirectCount,
                                              const uint32_t& cacheKey,
-                                             const nsCString& altDataType,
-                                             const bool& contentDecodingWillBeCalledOnParent) override;
+                                             const nsCString& altDataType) override;
   mozilla::ipc::IPCResult RecvOnTransportAndData(const nsresult& channelStatus,
                                                  const nsresult& status,
                                                  const uint64_t& offset,
                                                  const uint32_t& count,
                                                  const nsCString& data) override;
   mozilla::ipc::IPCResult RecvOnStopRequest(const nsresult& statusCode, const ResourceTimingStruct& timing) override;
   mozilla::ipc::IPCResult RecvOnProgress(const int64_t& progress, const int64_t& progressMax) override;
   mozilla::ipc::IPCResult RecvOnStatus(const nsresult& status) override;
@@ -269,18 +268,16 @@ private:
   // Set if the corresponding parent channel should force an interception to occur
   // before the network transaction is initiated.
   bool mShouldParentIntercept;
 
   // Set if the corresponding parent channel should suspend after a response
   // is synthesized.
   bool mSuspendParentAfterSynthesizeResponse;
 
-  bool mContentDecodingWillBeCalledOnParent;
-
   // Needed to call AsyncOpen in FinishInterceptedRedirect
   nsCOMPtr<nsIStreamListener> mInterceptedRedirectListener;
   nsCOMPtr<nsISupports> mInterceptedRedirectContext;
   // Needed to call CleanupRedirectingChannel in FinishInterceptedRedirect
   RefPtr<HttpChannelChild> mInterceptingChannel;
   // Used to call OverrideWithSynthesizedResponse in FinishInterceptedRedirect
   RefPtr<OverrideRunnable> mOverrideRunnable;
 

--- a/netwerk/protocol/http/HttpChannelParent.cpp
+++ b/netwerk/protocol/http/HttpChannelParent.cpp
@@ -61,17 +61,16 @@ HttpChannelParent::HttpChannelParent(con
   , mLoadContext(aLoadContext)
   , mStatus(NS_OK)
   , mPendingDiversion(false)
   , mDivertingFromChild(false)
   , mDivertedOnStartRequest(false)
   , mSuspendedForDiversion(false)
   , mSuspendAfterSynthesizeResponse(false)
   , mWillSynthesizeResponse(false)
-  , mWaitingForApplyConversionResponse(false)
   , mNestedFrameId(0)
 {
   LOG(("Creating HttpChannelParent [this=%p]\n", this));
 
   // Ensure gHttpHandler is initialized: we need the atom table up and running.
   nsCOMPtr<nsIHttpProtocolHandler> dummyInitializer =
     do_GetService(NS_NETWORK_PROTOCOL_CONTRACTID_PREFIX "http");
 
@@ -823,32 +822,16 @@ HttpChannelParent::RecvMarkOfflineCacheE
   if (mOfflineForeignMarker) {
     mOfflineForeignMarker->MarkAsForeign();
     mOfflineForeignMarker = 0;
   }
 
   return IPC_OK();
 }
 
-mozilla::ipc::IPCResult
-HttpChannelParent::RecvApplyConversion(const bool& aApply)
-{
-  LOG(("HttpChannelParent::RecvApplyConversion [this=%p, aApply=%d, "
-       "mWaitingForApplyConversionResponse=%d]",
-       this, aApply, mWaitingForApplyConversionResponse));
-  MOZ_ASSERT(mChannel->HasListenerForTraceableChannel());
-  if (mWaitingForApplyConversionResponse) {
-    mWaitingForApplyConversionResponse = false;
-    mChannel->SetApplyConversion(aApply);
-    mChannel->ApplyContentConversions();
-    mChannel->Resume();
-  }
-  return IPC_OK();
-}
-
 class DivertDataAvailableEvent : public ChannelEvent
 {
 public:
   DivertDataAvailableEvent(HttpChannelParent* aParent,
                            const nsCString& data,
                            const uint64_t& offset,
                            const uint32_t& count)
   : mParent(aParent)
@@ -1154,16 +1137,20 @@ HttpChannelParent::OnStartRequest(nsIReq
     appCache->GetClientID(appCacheClientId);
     if (mIPCClosed ||
         !SendAssociateApplicationCache(appCacheGroupId, appCacheClientId))
     {
       return NS_ERROR_UNEXPECTED;
     }
   }
 
+  nsCOMPtr<nsIEncodedChannel> encodedChannel = do_QueryInterface(aRequest);
+  if (encodedChannel)
+    encodedChannel->SetApplyConversion(false);
+
   // Keep the cache entry for future use in RecvSetCacheTokenCachedCharset().
   // It could be already released by nsHttpChannel at that time.
   nsCOMPtr<nsISupports> cacheEntry;
   chan->GetCacheToken(getter_AddRefs(cacheEntry));
   mCacheEntry = do_QueryInterface(cacheEntry);
 
   nsresult channelStatus = NS_OK;
   chan->GetStatus(&channelStatus);
@@ -1187,54 +1174,32 @@ HttpChannelParent::OnStartRequest(nsIReq
     if (NS_FAILED(rv)) {
       return rv;
     }
   }
 
   nsAutoCString altDataType;
   chan->GetAlternativeDataType(altDataType);
 
-  nsCOMPtr<nsIEncodedChannel> encodedChannel = do_QueryInterface(aRequest);
-  if (encodedChannel) {
-    encodedChannel->SetApplyConversion(false);
-    if (mChannel->HasListenerForTraceableChannel()) {
-      LOG(("HttpChannelParent::OnStartRequest - suspend channel until we know "
-           "whether we need to apply conversions [this=%p]\n", this));
-      // We have a traceableChannel listener so we need to do a data conversion
-      // on the parent.
-      // The correct decision whether we need to convert the data is made on
-      // the child process during OnStartRequest call, therefore we will
-      // suspend the channel here and wait for the decision result from the
-      // child (we are waiting for RecvApplyConversion).
-      mWaitingForApplyConversionResponse = NS_SUCCEEDED(mChannel->Suspend()) ?
-                                           true : false;
-    }
-  }
-
   // !!! We need to lock headers and please don't forget to unlock them !!!
   requestHead->Enter();
   nsresult rv = NS_OK;
   if (mIPCClosed ||
       !SendOnStartRequest(channelStatus,
                           responseHead ? *responseHead : nsHttpResponseHead(),
                           !!responseHead,
                           requestHead->Headers(),
                           isFromCache,
                           mCacheEntry ? true : false,
                           expirationTime, cachedCharset, secInfoSerialization,
                           chan->GetSelfAddr(), chan->GetPeerAddr(),
                           redirectCount,
                           cacheKeyValue,
-                          altDataType,
-                          mWaitingForApplyConversionResponse))
+                          altDataType))
   {
-    if (mWaitingForApplyConversionResponse) {
-      mChannel->Resume();
-      mWaitingForApplyConversionResponse = false;
-    }
     rv = NS_ERROR_UNEXPECTED;
   }
   requestHead->Exit();
   return rv;
 }
 
 NS_IMETHODIMP
 HttpChannelParent::OnStopRequest(nsIRequest *aRequest,
@@ -1664,35 +1629,24 @@ HttpChannelParent::StartDiversion()
         mChannel->Cancel(rv);
       }
       mStatus = rv;
     }
   }
   mDivertedOnStartRequest = true;
 
   // After OnStartRequest has been called, setup content decoders if needed.
-  if (mWaitingForApplyConversionResponse) {
-    // If we are mWaitingForApplyConversionResponse, means that mChannel is
-    // suspended right after OnStartRequest, therefore we can apply content
-    // conversion directly on the top of mChannel and Tracable Listeners will
-    // get decoded data.
-    if (NS_SUCCEEDED(mStatus)) {
-      mChannel->ApplyContentConversions();
-    }
-    mWaitingForApplyConversionResponse = false;
-    mChannel->Resume();
-  } else {
-    // Create a content conversion chain based on mDivertListener and update
-    // mDivertListener.
-    nsCOMPtr<nsIStreamListener> converterListener;
-    mChannel->DoApplyContentConversions(mDivertListener,
-                                        getter_AddRefs(converterListener));
-    if (converterListener) {
-      mDivertListener = converterListener.forget();
-    }
+  //
+  // Create a content conversion chain based on mDivertListener and update
+  // mDivertListener.
+  nsCOMPtr<nsIStreamListener> converterListener;
+  mChannel->DoApplyContentConversions(mDivertListener,
+                                      getter_AddRefs(converterListener));
+  if (converterListener) {
+    mDivertListener = converterListener.forget();
   }
 
   // Now mParentListener can be diverted to mDivertListener.
   DebugOnly<nsresult> rvdbg = mParentListener->DivertTo(mDivertListener);
   MOZ_ASSERT(NS_SUCCEEDED(rvdbg));
   mDivertListener = nullptr;
 
   if (NS_WARN_IF(mIPCClosed || !SendFlushedForDiversion())) {
@@ -1753,21 +1707,16 @@ HttpChannelParent::NotifyDiversionFailed
        this, static_cast<uint32_t>(aErrorCode)));
   MOZ_RELEASE_ASSERT(NS_FAILED(aErrorCode));
   MOZ_RELEASE_ASSERT(mDivertingFromChild);
   MOZ_RELEASE_ASSERT(mParentListener);
   MOZ_RELEASE_ASSERT(mChannel);
 
   mChannel->Cancel(aErrorCode);
 
-  if (mWaitingForApplyConversionResponse) {
-    mWaitingForApplyConversionResponse = false;
-    mChannel->Resume();
-  }
-
   mChannel->ForcePending(false);
 
   bool isPending = false;
   nsresult rv = mChannel->IsPending(&isPending);
   MOZ_RELEASE_ASSERT(NS_SUCCEEDED(rv));
 
   // Resume only if we suspended earlier.
   if (mSuspendedForDiversion) {

--- a/netwerk/protocol/http/HttpChannelParent.h
+++ b/netwerk/protocol/http/HttpChannelParent.h
@@ -170,17 +170,16 @@ protected:
   virtual mozilla::ipc::IPCResult RecvMarkOfflineCacheEntryAsForeign() override;
   virtual mozilla::ipc::IPCResult RecvDivertOnDataAvailable(const nsCString& data,
                                          const uint64_t& offset,
                                          const uint32_t& count) override;
   virtual mozilla::ipc::IPCResult RecvDivertOnStopRequest(const nsresult& statusCode) override;
   virtual mozilla::ipc::IPCResult RecvDivertComplete() override;
   virtual mozilla::ipc::IPCResult RecvRemoveCorsPreflightCacheEntry(const URIParams& uri,
                                                                     const mozilla::ipc::PrincipalInfo& requestingPrincipal) override;
-  virtual mozilla::ipc::IPCResult RecvApplyConversion(const bool& applyConversion)  override;
   virtual void ActorDestroy(ActorDestroyReason why) override;
 
   // Supporting function for ADivertableParentChannel.
   nsresult ResumeForDiversion();
 
   // Asynchronously calls NotifyDiversionFailed.
   void FailDiversion(nsresult aErrorCode, bool aSkipResume = true);
 
@@ -255,36 +254,16 @@ private:
 
   bool mSuspendedForDiversion;
 
   // Set if this channel should be suspended after synthesizing a response.
   bool mSuspendAfterSynthesizeResponse;
   // Set if this channel will synthesize its response.
   bool mWillSynthesizeResponse;
 
-  // Whether we need to apply a data conversion or not is decided during
-  // a OnStartRequest call on the last channel listener. This is perform on the
-  // child and conversion is perform on the child process as well.
-  // If the http channel has a TracableChannel listener we need to perform
-  // the data conversion, if needed, on the parent, but still the decision
-  // whether to perform the conversion or not is made during OnStartRequest on
-  // the child process. Using a parameter in SendOnStartRequest we will request
-  // from the child to send us the final decision (Send/RecvApplyConversion
-  // with parameter aApply true or false). The mChannel will be suspended until
-  // the responce is received.
-  // If the channel gets canceled we will just set the ApplyConversion to
-  // false and resume mChannel.
-  //
-  // If DivertToParent is performed, the OnStartRequest call on the last
-  // channel listener is performed on the parent and the child process does not
-  // need to send Send/RecvApplyConversion. ApplyContentConversions will be
-  // called after the OnStartRequest has been called (This is in the
-  // StartDiversion function on the parent).
-  bool mWaitingForApplyConversionResponse;
-
   dom::TabId mNestedFrameId;
 
   RefPtr<ChannelEventQueue> mEventQ;
 };
 
 NS_DEFINE_STATIC_IID_ACCESSOR(HttpChannelParent,
                               HTTP_CHANNEL_PARENT_IID)
 

--- a/netwerk/protocol/http/PHttpChannel.ipdl
+++ b/netwerk/protocol/http/PHttpChannel.ipdl
@@ -86,36 +86,33 @@ parent:
   // to remove any matching entry from the CORS preflight cache.
   async RemoveCorsPreflightCacheEntry(URIParams uri,
                                       PrincipalInfo requestingPrincipal);
 
   // After receiving this message, the parent calls SendDeleteSelf, and makes
   // sure not to send any more messages after that.
   async DeletingChannel();
 
-  async ApplyConversion(bool applyConversion);
-
   async __delete__();
 
 child:
   async OnStartRequest(nsresult            channelStatus,
                        nsHttpResponseHead  responseHead,
                        bool                useResponseHead,
                        nsHttpHeaderArray   requestHeaders,
                        bool                isFromCache,
                        bool                cacheEntryAvailable,
                        uint32_t            cacheExpirationTime,
                        nsCString           cachedCharset,
                        nsCString           securityInfoSerialization,
                        NetAddr             selfAddr,
                        NetAddr             peerAddr,
                        int16_t             redirectCount,
                        uint32_t            cacheKey,
-                       nsCString           altDataType,
-                       bool                contentDecodingWillBeCalledOnParent);
+                       nsCString           altDataType);
 
   // Combines a single OnDataAvailable and its associated OnProgress &
   // OnStatus calls into one IPDL message
   async OnTransportAndData(nsresult  channelStatus,
                            nsresult  transportStatus,
                            uint64_t  offset,
                            uint32_t  count,
                            nsCString data);

--- a/netwerk/protocol/http/nsHttpChannel.cpp
+++ b/netwerk/protocol/http/nsHttpChannel.cpp
@@ -281,17 +281,16 @@ nsHttpChannel::nsHttpChannel()
     , mIsPartialRequest(0)
     , mHasAutoRedirectVetoNotifier(0)
     , mPinCacheContent(0)
     , mIsCorsPreflightDone(0)
     , mStronglyFramed(false)
     , mPushedStream(nullptr)
     , mLocalBlocklist(false)
     , mWarningReporter(nullptr)
-    , mDelayedInstallCacheListenerForTraceableChannel(false)
     , mIsReadingFromCache(false)
     , mOnCacheAvailableCalled(false)
     , mRacingNetAndCache(false)
     , mDidReval(false)
 {
     LOG(("Creating nsHttpChannel [this=%p]\n", this));
     mChannelCreationTime = PR_Now();
     mChannelCreationTimestamp = TimeStamp::Now();
@@ -1254,38 +1253,16 @@ EnsureMIMEOfScript(nsIURI* aURI, nsHttpR
         return NS_OK;
     }
 
     // script load has unknown type
     Telemetry::Accumulate(Telemetry::SCRIPT_BLOCK_INCORRECT_MIME, 0);
     return NS_OK;
 }
 
-void
-nsHttpChannel::ApplyContentConversions()
-{
-    nsCOMPtr<nsIStreamListener> listener;
-    nsISupports *ctxt = mListenerContext;
-    nsresult rv = DoApplyContentConversions(mListener, getter_AddRefs(listener), ctxt);
-    if (NS_FAILED(rv)) {
-        AsyncAbort(rv);
-    }
-    if (listener) {
-        mListener = listener;
-        mCompressListener = listener;
-    }
-
-    if (mDelayedInstallCacheListenerForTraceableChannel &&
-        mCacheEntry && !mCacheEntryIsReadOnly) {
-        nsresult rv = InstallCacheListener();
-        if (NS_FAILED(rv)) {
-            AsyncAbort(rv);
-        }
-    }
-}
 
 nsresult
 nsHttpChannel::CallOnStartRequest()
 {
     MOZ_RELEASE_ASSERT(!(mRequireCORSPreflight &&
                          mInterceptCache != INTERCEPTED) ||
                        mIsCorsPreflightDone,
                        "CORS preflight must have been finished by the time we "
@@ -2483,20 +2460,16 @@ nsHttpChannel::ContinueProcessNormal(nsr
         }
     }
 
     rv = CallOnStartRequest();
     if (NS_FAILED(rv)) return rv;
 
     // install cache listener if we still have a cache entry open
     if (mCacheEntry && !mCacheEntryIsReadOnly) {
-        if (mHasListenerForTraceableChannel) {
-            mDelayedInstallCacheListenerForTraceableChannel = true;
-            return NS_OK;
-        }
         rv = InstallCacheListener();
         if (NS_FAILED(rv)) return rv;
     }
 
     return NS_OK;
 }
 
 nsresult

--- a/netwerk/protocol/http/nsHttpChannel.h
+++ b/netwerk/protocol/http/nsHttpChannel.h
@@ -177,18 +177,16 @@ public:
     NS_IMETHOD OnPreflightFailed(nsresult aError) override;
 
     nsresult AddSecurityMessage(const nsAString& aMessageTag,
                                 const nsAString& aMessageCategory) override;
 
     void SetWarningReporter(HttpChannelSecurityWarningReporter* aReporter)
       { mWarningReporter = aReporter; }
 
-    void ApplyContentConversions();
-
 public: /* internal necko use only */
 
     void InternalSetUploadStream(nsIInputStream *uploadStream)
       { mUploadStream = uploadStream; }
     void SetUploadStreamHasHeaders(bool hasHeaders)
       { mUploadStreamHasHeaders = hasHeaders; }
 
     nsresult SetReferrerWithPolicyInternal(nsIURI *referrer,
@@ -609,23 +607,16 @@ private:
 
     nsCString mUsername;
 
     // If non-null, warnings should be reported to this object.
     HttpChannelSecurityWarningReporter* mWarningReporter;
 
     RefPtr<ADivertableParentChannel> mParentChannel;
 
-    // If a cache listener needs to be installed, it needs to be install after
-    // DoApplyContentConversions is called (this is because the cache needs to
-    // receive not converted data). If a channel has a nsITracableListener call
-    // to DoApplyContentConversions will be delayed so we need to delay the
-    // InstallCacheListener call as well.
-    uint32_t mDelayedInstallCacheListenerForTraceableChannel : 1;
-
     // True if the channel is reading from cache.
     Atomic<bool> mIsReadingFromCache;
 
     // These next members are only used in unit tests to delay the call to
     // cache->AsyncOpenURI in order to race the cache with the network.
     nsCOMPtr<nsITimer> mCacheOpenTimer;
     nsCOMPtr<nsIRunnable> mCacheOpenRunnable;
     uint32_t mCacheOpenDelay = 0;

deleted file mode 100644
--- a/netwerk/test/unit_ipc/child_tracable_listener.js
+++ /dev/null
@@ -1,36 +0,0 @@
-/**
- * Send HTTP requests and check if the received content is correct.
- */
-
-Cu.import("resource://gre/modules/NetUtil.jsm");
-
-let shouldQuit = false;
-
-function run_test() {
-  // keep the event loop busy and the test alive until a "finish" command
-  // is issued by parent
-  do_timeout(100, function keepAlive() {
-    if (!shouldQuit) {
-      do_timeout(100, keepAlive);
-    }
-  });
-}
-
-var expectedResponse;
-
-function makeRequest(uri, response) {
-  let requestChannel = NetUtil.newChannel({uri, loadUsingSystemPrincipal: true});
-
-  expectedResponse = response;
-  requestChannel.asyncOpen2(new ChannelListener(checkResponse, null, CL_EXPECT_GZIP));
-}
-
-function checkResponse(request, buffer) {
-  do_check_eq(expectedResponse, buffer);
-
-  do_send_remote_message(`response`);
-}
-
-function finish() {
-  shouldQuit = true;
-}

deleted file mode 100644
--- a/netwerk/test/unit_ipc/test_traceable_channel_decoded_data.js
+++ /dev/null
@@ -1,172 +0,0 @@
-// Test nsITraceableChannel interface.
-//
-// The test checks that content-encoded responses are received decoded by a
-// tracing listener.
-
-Cu.import("resource://testing-common/httpd.js");
-Cu.import("resource://gre/modules/NetUtil.jsm");
-
-const DEBUG = false;
-
-function debug(msg) {
-  if (DEBUG) {
-    dump(msg);
-  }
-}
-
-var httpserver = new HttpServer();
-httpserver.start(-1);
-const PORT = httpserver.identity.primaryPort;
-
-var originalBody = "original http response body";
-
-var body = [
-  0x1f, 0x8b, 0x08, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x03, 0xcb, 0x2f, 0xca, 0x4c, 0xcf, 0xcc,
-  0x4b, 0xcc, 0x51, 0xc8, 0x28, 0x29, 0x29, 0x50, 0x28, 0x4a, 0x2d, 0x2e, 0xc8, 0xcf, 0x2b, 0x4e,
-  0x55, 0x48, 0xca, 0x4f, 0xa9, 0x04, 0x00, 0x94, 0xde, 0x94, 0x9c, 0x1b, 0x00, 0x00, 0x00];
-
-var observer;
-
-function TracingListener() {}
-
-TracingListener.prototype = {
-  gotOnStartRequest: false,
-  pipe: null,
-  streamSink: null,
-  listener: null,
-
-  // Replace received response body.
-  onDataAvailable: function(request, context, inputStream,
-                           offset, count) {
-    debug("*** tracing listener onDataAvailable\n");
-  },
-
-  onStartRequest: function(request, context) {
-    debug("*** tracing listener onStartRequest\n");
-
-    this.gotOnStartRequest = true;
-
-    request.QueryInterface(Components.interfaces.nsIHttpChannelInternal);
-
-    do_check_eq(request.localAddress, "127.0.0.1");
-    do_check_eq(request.localPort > 0, true);
-    do_check_neq(request.localPort, PORT);
-    do_check_eq(request.remoteAddress, "127.0.0.1");
-    do_check_eq(request.remotePort, PORT);
-  },
-
-  onStopRequest: function(request, context, statusCode) {
-    debug("*** tracing listener onStopRequest\n");
-
-    var sin = Components.classes["@mozilla.org/scriptableinputstream;1"].
-                createInstance(Ci.nsIScriptableInputStream);
-
-    this.streamSink.close();
-    var input = this.pipe.inputStream;
-    sin.init(input);
-    do_check_eq(sin.available(), originalBody.length);
-
-    var result = sin.read(originalBody.length);
-    do_check_eq(result, originalBody);
-
-    input.close();
-
-    do_check_eq(this.gotOnStartRequest, true);
-
-    let message = `response`;
-    do_await_remote_message(message).then(() => {
-      sendCommand("finish();", stopServer);
-    });
-  },
-
-  QueryInterface: function(iid) {
-    if (iid.equals(Components.interfaces.nsIStreamListener) ||
-        iid.equals(Components.interfaces.nsIRequestObserver) ||
-        iid.equals(Components.interfaces.nsISupports)
-        )
-      return this;
-    throw Components.results.NS_NOINTERFACE;
-  }
-}
-
-function HttpResponseExaminer() {}
-
-HttpResponseExaminer.prototype = {
-  register: function() {
-    Cc["@mozilla.org/observer-service;1"].
-      getService(Components.interfaces.nsIObserverService).
-      addObserver(this, "http-on-examine-response", true);
-    debug("Did HttpResponseExaminer.register\n");
-  },
-
-  unregister: function() {
-    Cc["@mozilla.org/observer-service;1"].
-      getService(Components.interfaces.nsIObserverService).
-      removeObserver(this, "http-on-examine-response", true);
-    debug("Did HttpResponseExaminer.unregister\n");
-  },
-
-  // Replace channel's listener.
-  observe: function(subject, topic, data) {
-    debug("In HttpResponseExaminer.observe\n");
-
-    try {
-      subject.QueryInterface(Components.interfaces.nsITraceableChannel);
-
-      var tee = Cc["@mozilla.org/network/stream-listener-tee;1"].
-          createInstance(Ci.nsIStreamListenerTee);
-      var newListener = new TracingListener();
-      newListener.pipe = Cc["@mozilla.org/pipe;1"].createInstance(Ci.nsIPipe);
-      newListener.pipe.init(false, false, 0, 0xffffffff, null);
-      newListener.streamSink = newListener.pipe.outputStream;
-
-      var originalListener = subject.setNewListener(tee);
-      tee.init(originalListener, newListener.streamSink, newListener);
-    } catch(e) {
-      do_throw("can't replace listener " + e);
-    }
-
-    debug("Did HttpResponseExaminer.observe\n");
-  },
-
-  QueryInterface: function(iid) {
-    if (iid.equals(Components.interfaces.nsIObserver) ||
-        iid.equals(Components.interfaces.nsISupportsWeakReference) ||
-        iid.equals(Components.interfaces.nsISupports))
-      return this;
-    throw Components.results.NS_NOINTERFACE;
-  }
-}
-
-function test_handlerContentEncoded(metadata, response) {
-  response.setStatusLine(metadata.httpVersion, 200, "OK");
-  response.setHeader("Content-Type", "text/plain", false);
-  response.setHeader("Content-Encoding", "gzip", false);
-  response.setHeader("Content-Length", "" + body.length, false);
-
-  var bos = Components.classes["@mozilla.org/binaryoutputstream;1"]
-    .createInstance(Components.interfaces.nsIBinaryOutputStream);
-  bos.setOutputStream(response.bodyOutputStream);
-
-  response.processAsync();
-  bos.writeByteArray(body, body.length);
-  response.finish();
-}
-
-function test_contentEncoded() {
-  sendCommand(`makeRequest("http://localhost:${PORT}/testContentEncoded", "${originalBody}");`);
-}
-
-function stopServer() {
-  observer.unregister();
-  httpserver.stop(do_test_finished)
-}
-
-function run_test() {
-
-  observer = new HttpResponseExaminer();
-  observer.register();
-
-  httpserver.registerPathHandler("/testContentEncoded", test_handlerContentEncoded);
-  run_test_in_child("child_tracable_listener.js", test_contentEncoded);
-}

deleted file mode 100644
--- a/netwerk/test/unit_ipc/test_traceable_channel_modify_response.js
+++ /dev/null
@@ -1,186 +0,0 @@
-// Test nsITraceableChannel interface.
-//
-// The test checks that a tracing listener can modifies the body of a HTTP
-// response.
-// This test also check that it is not possible to set a tracableLisener after
-// onStartRequest is called.
-
-Cu.import("resource://testing-common/httpd.js");
-Cu.import("resource://gre/modules/NetUtil.jsm");
-
-const DEBUG = false;
-
-function debug(msg) {
-  if (DEBUG) {
-    dump(msg);
-  }
-}
-
-var httpserver = new HttpServer();
-httpserver.start(-1);
-const PORT = httpserver.identity.primaryPort;
-
-var originalBody = "original http response body";
-var replacedBody = "replaced http response body";
-
-var observer;
-
-function TracingListener() {}
-
-TracingListener.prototype = {
-  gotOnStartRequest: false,
-  pipe: null,
-  streamSink: null,
-  listener: null,
-  onDataAvailableCalled: false,
-
-  // Replace received response body.
-  onDataAvailable: function(request, context, inputStream,
-                           offset, count) {
-    debug("*** tracing listener onDataAvailable\n");
-
-    var binaryInputStream = Cc["@mozilla.org/binaryinputstream;1"].
-      createInstance(Components.interfaces.nsIBinaryInputStream);
-    binaryInputStream.setInputStream(inputStream);
-
-    var data = binaryInputStream.readBytes(count);
-    var origBody = originalBody.substr(offset, count);
-
-    do_check_eq(origBody, data);
-
-    if (!this.onDataAvailableCalled) {
-      this.onDataAvailableCalled = true;
-      var storageStream = Cc["@mozilla.org/storagestream;1"].
-        createInstance(Components.interfaces.nsIStorageStream);
-      var binaryOutputStream = Cc["@mozilla.org/binaryoutputstream;1"].
-        createInstance(Components.interfaces.nsIBinaryOutputStream);
-
-      storageStream.init(8192, 100, null);
-      binaryOutputStream.setOutputStream(storageStream.getOutputStream(0));
-
-      var newBody = replacedBody.substr(offset, count);
-      binaryOutputStream.writeBytes(newBody, newBody.length);
-
-      this.listener.onDataAvailable(request, context,
-                                    storageStream.newInputStream(0), 0,
-                                    replacedBody.length);
-    }
-  },
-
-  onStartRequest: function(request, context) {
-    debug("*** tracing listener onStartRequest\n");
-
-    this.listener.onStartRequest(request, context);
-
-    this.gotOnStartRequest = true;
-
-    request.QueryInterface(Components.interfaces.nsIHttpChannelInternal);
-
-    do_check_eq(request.localAddress, "127.0.0.1");
-    do_check_eq(request.localPort > 0, true);
-    do_check_neq(request.localPort, PORT);
-    do_check_eq(request.remoteAddress, "127.0.0.1");
-    do_check_eq(request.remotePort, PORT);
-
-    // Make sure listener can't be replaced after OnStartRequest was called.
-    request.QueryInterface(Components.interfaces.nsITraceableChannel);
-    try {
-      var newListener = new TracingListener();
-      newListener.listener = request.setNewListener(newListener);
-    } catch(e) {
-      do_check_true(true, "TracingListener.onStartRequest swallowing exception: " + e + "\n");
-      return; // OK
-    }
-    do_throw("replaced channel's listener during onStartRequest.");
-  },
-
-  onStopRequest: function(request, context, statusCode) {
-    debug("*** tracing listener onStopRequest\n");
-
-
-    this.listener.onStopRequest(request, context, statusCode)
-
-    do_check_eq(this.gotOnStartRequest, true);
-
-    let message = `response`;
-    do_await_remote_message(message).then(() => {
-      sendCommand("finish();", stopServer);
-    });
-  },
-
-  QueryInterface: function(iid) {
-    if (iid.equals(Components.interfaces.nsIStreamListener) ||
-        iid.equals(Components.interfaces.nsIRequestObserver) ||
-        iid.equals(Components.interfaces.nsISupports)
-        )
-      return this;
-    throw Components.results.NS_NOINTERFACE;
-  }
-}
-
-function HttpResponseExaminer() {}
-
-HttpResponseExaminer.prototype = {
-  register: function() {
-    Cc["@mozilla.org/observer-service;1"].
-      getService(Components.interfaces.nsIObserverService).
-      addObserver(this, "http-on-examine-response", true);
-    debug("Did HttpResponseExaminer.register\n");
-  },
-
-  unregister: function() {
-    Cc["@mozilla.org/observer-service;1"].
-      getService(Components.interfaces.nsIObserverService).
-      removeObserver(this, "http-on-examine-response", true);
-    debug("Did HttpResponseExaminer.unregister\n");
-  },
-
-  // Replace channel's listener.
-  observe: function(subject, topic, data) {
-    debug("In HttpResponseExaminer.observe\n");
-
-    try {
-      subject.QueryInterface(Components.interfaces.nsITraceableChannel);
-      var newListener = new TracingListener();
-      newListener.listener = subject.setNewListener(newListener);
-    } catch(e) {
-      do_throw("can't replace listener " + e);
-    }
-
-    debug("Did HttpResponseExaminer.observe\n");
-  },
-
-  QueryInterface: function(iid) {
-    if (iid.equals(Components.interfaces.nsIObserver) ||
-        iid.equals(Components.interfaces.nsISupportsWeakReference) ||
-        iid.equals(Components.interfaces.nsISupports))
-      return this;
-    throw Components.results.NS_NOINTERFACE;
-  }
-}
-
-function test_handlerSimple(metadata, response) {
-  response.setHeader("Content-Type", "text/html", false);
-  response.setStatusLine(metadata.httpVersion, 200, "OK");
-  response.bodyOutputStream.write(originalBody, originalBody.length);
-}
-
-function test_modify() { 
-  sendCommand(`makeRequest("http://localhost:${PORT}/testSimple", "${replacedBody}");`);
-}
-
-
-function stopServer() {
-  observer.unregister();
-  httpserver.stop(do_test_finished)
-}
-
-function run_test() {
-
-  observer = new HttpResponseExaminer();
-  observer.register();
-
-  httpserver.registerPathHandler("/testSimple", test_handlerSimple);
-
-  run_test_in_child("child_tracable_listener.js", test_modify);
-}

--- a/netwerk/test/unit_ipc/xpcshell.ini
+++ b/netwerk/test/unit_ipc/xpcshell.ini
@@ -1,14 +1,13 @@
 [DEFAULT]
 head = head_channels_clone.js head_cc.js
 skip-if = toolkit == 'android'
 support-files =
   child_channel_id.js
-  child_tracable_listener.js
   !/netwerk/test/unit/test_XHR_redirects.js
   !/netwerk/test/unit/test_bug248970_cookie.js
   !/netwerk/test/unit/test_bug528292.js
   !/netwerk/test/unit/test_cache_jar.js
   !/netwerk/test/unit/test_cacheflags.js
   !/netwerk/test/unit/test_channel_close.js
   !/netwerk/test/unit/test_cookie_header.js
   !/netwerk/test/unit/test_cookiejars.js
@@ -93,12 +92,10 @@ skip-if = true
 [test_XHR_redirects.js]
 [test_redirect_history_wrap.js]
 [test_reply_without_content_type_wrap.js]
 [test_getHost_wrap.js]
 [test_alt-data_simple_wrap.js]
 [test_alt-data_stream_wrap.js]
 [test_original_sent_received_head_wrap.js]
 [test_channel_id.js]
-[test_traceable_channel_modify_response.js]
-[test_traceable_channel_decoded_data.js]
 [test_trackingProtection_annotateChannels_wrap1.js]
 [test_trackingProtection_annotateChannels_wrap2.js]