diff --git a/dom/ipc/ContentParent.cpp b/dom/ipc/ContentParent.cpp
index b13a8b6fdf84..710776d58cb6 100644
--- a/dom/ipc/ContentParent.cpp
+++ b/dom/ipc/ContentParent.cpp
@@ -5383,19 +5383,3 @@ ContentParent::RecvDeviceReset()
 
   return IPC_OK();
 }
-
-mozilla::ipc::IPCResult
-ContentParent::RecvBHRThreadHang(const HangDetails& aDetails)
-{
-  nsCOMPtr<nsIObserverService> obs = mozilla::services::GetObserverService();
-  if (obs) {
-    // Copy the HangDetails recieved over the network into a nsIHangDetails, and
-    // then fire our own observer notification.
-    // XXX: We should be able to avoid this potentially expensive copy here by
-    // moving our deserialized argument.
-    nsCOMPtr<nsIHangDetails> hangDetails =
-      new nsHangDetails(HangDetails(aDetails));
-    obs->NotifyObservers(hangDetails, "bhr-thread-hang", nullptr);
-  }
-  return IPC_OK();
-}
diff --git a/dom/ipc/ContentParent.h b/dom/ipc/ContentParent.h
index a783456de8ce..254798a98dab 100644
--- a/dom/ipc/ContentParent.h
+++ b/dom/ipc/ContentParent.h
@@ -1149,9 +1149,6 @@ private:
     nsTArray<ChildEventData>&& events) override;
   virtual mozilla::ipc::IPCResult RecvRecordDiscardedData(
     const DiscardedData& aDiscardedData) override;
-
-  virtual mozilla::ipc::IPCResult RecvBHRThreadHang(
-    const HangDetails& aHangDetails) override;
 public:
   void SendGetFilesResponseAndForget(const nsID& aID,
                                      const GetFilesResponseResult& aResult);
diff --git a/dom/ipc/PContent.ipdl b/dom/ipc/PContent.ipdl
index e5269f62e9c2..469d1b58a9ee 100644
--- a/dom/ipc/PContent.ipdl
+++ b/dom/ipc/PContent.ipdl
@@ -96,7 +96,6 @@ using mozilla::Telemetry::KeyedScalarAction from "mozilla/TelemetryComms.h";
 using mozilla::Telemetry::ChildEventData from "mozilla/TelemetryComms.h";
 using mozilla::Telemetry::DiscardedData from "mozilla/TelemetryComms.h";
 using mozilla::CrossProcessMutexHandle from "mozilla/ipc/CrossProcessMutex.h";
-using mozilla::HangDetails from "mozilla/HangDetails.h";
 
 union ChromeRegistryItem
 {
@@ -1056,8 +1055,6 @@ parent:
     async FinishMemoryReport(uint32_t aGeneration);
 
     async MaybeReloadPlugins();
-
-    async BHRThreadHang(HangDetails aHangDetails);
 both:
      async AsyncMessage(nsString aMessage, CpowEntry[] aCpows,
                         Principal aPrincipal, ClonedMessageData aData);
diff --git a/gfx/ipc/GPUChild.cpp b/gfx/ipc/GPUChild.cpp
index 72cb3b747698..953f1b6be479 100644
--- a/gfx/ipc/GPUChild.cpp
+++ b/gfx/ipc/GPUChild.cpp
@@ -20,7 +20,6 @@
 #include "mozilla/ipc/CrashReporterHost.h"
 #include "mozilla/layers/LayerTreeOwnerTracker.h"
 #include "mozilla/Unused.h"
-#include "nsIObserverService.h"
 
 #ifdef MOZ_GECKO_PROFILER
 #include "ProfilerParent.h"
@@ -288,22 +287,6 @@ GPUChild::RecvUsedFallback(const Fallback& aFallback, const nsCString& aMessage)
   return IPC_OK();
 }
 
-mozilla::ipc::IPCResult
-GPUChild::RecvBHRThreadHang(const HangDetails& aDetails)
-{
-  nsCOMPtr<nsIObserverService> obs = mozilla::services::GetObserverService();
-  if (obs) {
-    // Copy the HangDetails recieved over the network into a nsIHangDetails, and
-    // then fire our own observer notification.
-    // XXX: We should be able to avoid this potentially expensive copy here by
-    // moving our deserialized argument.
-    nsCOMPtr<nsIHangDetails> hangDetails =
-      new nsHangDetails(HangDetails(aDetails));
-    obs->NotifyObservers(hangDetails, "bhr-thread-hang", nullptr);
-  }
-  return IPC_OK();
-}
-
 class DeferredDeleteGPUChild : public Runnable
 {
 public:
diff --git a/gfx/ipc/GPUChild.h b/gfx/ipc/GPUChild.h
index 0f45bc45713f..9e4f6063272f 100644
--- a/gfx/ipc/GPUChild.h
+++ b/gfx/ipc/GPUChild.h
@@ -60,7 +60,6 @@ public:
   mozilla::ipc::IPCResult RecvFinishMemoryReport(const uint32_t& aGeneration) override;
   mozilla::ipc::IPCResult RecvUpdateFeature(const Feature& aFeature, const FeatureFailure& aChange) override;
   mozilla::ipc::IPCResult RecvUsedFallback(const Fallback& aFallback, const nsCString& aMessage) override;
-  mozilla::ipc::IPCResult RecvBHRThreadHang(const HangDetails& aDetails) override;
 
   bool SendRequestMemoryReport(const uint32_t& aGeneration,
                                const bool& aAnonymize,
diff --git a/gfx/ipc/PGPU.ipdl b/gfx/ipc/PGPU.ipdl
index bb667cce46ad..120c494f349a 100644
--- a/gfx/ipc/PGPU.ipdl
+++ b/gfx/ipc/PGPU.ipdl
@@ -23,7 +23,6 @@ using mozilla::Telemetry::ChildEventData from "mozilla/TelemetryComms.h";
 using mozilla::Telemetry::DiscardedData from "mozilla/TelemetryComms.h";
 using mozilla::gfx::Feature from "gfxFeature.h";
 using mozilla::gfx::Fallback from "gfxFallback.h";
-using mozilla::HangDetails from "mozilla/HangDetails.h";
 
 namespace mozilla {
 namespace gfx {
@@ -125,8 +124,6 @@ child:
 
   // Notify about:support/Telemetry that a fallback occurred.
   async UsedFallback(Fallback aFallback, nsCString message);
-
-  async BHRThreadHang(HangDetails aDetails);
 };
 
 } // namespace gfx
diff --git a/toolkit/components/backgroundhangmonitor/HangDetails.cpp b/toolkit/components/backgroundhangmonitor/HangDetails.cpp
index 0fc596256bc7..e87ac80a3982 100644
--- a/toolkit/components/backgroundhangmonitor/HangDetails.cpp
+++ b/toolkit/components/backgroundhangmonitor/HangDetails.cpp
@@ -200,32 +200,6 @@ nsHangDetails::Submit()
     if (os) {
       os->NotifyObservers(hangDetails, "bhr-thread-hang", nullptr);
     }
-
-    // If we're not in the parent process, we might need to transmit our hang
-    // details to another process, so that they can be reported there.
-    switch (XRE_GetProcessType()) {
-    case GeckoProcessType_Content: {
-      auto cc = dom::ContentChild::GetSingleton();
-      if (cc) {
-        Unused << cc->SendBHRThreadHang(hangDetails->mDetails);
-      }
-      break;
-    }
-    case GeckoProcessType_GPU: {
-      auto gp = gfx::GPUParent::GetSingleton();
-      if (gp) {
-        Unused << gp->SendBHRThreadHang(hangDetails->mDetails);
-      }
-      break;
-    }
-    case GeckoProcessType_Default:
-      break;
-    default:
-      // XXX: Consider handling GeckoProcessType_GMPlugin and
-      // GeckoProcessType_Plugin?
-      NS_WARNING("Unsupported BHR process type - discarding hang.");
-      break;
-    }
   });
 
   nsresult rv = SystemGroup::Dispatch(TaskCategory::Other,
@@ -266,19 +240,21 @@ ParamTraits<mozilla::HangDetails>::Write(Message* aMsg, const mozilla::HangDetai
   WriteParam(aMsg, aParam.mPseudoStack);
 
   // Write out the annotation information
-  {
-    // If we have no annotations, write out a 0-length annotations.
-    if (!aParam.mAnnotations) {
-      WriteParam(aMsg, 0);
-    }
+  // If we have no annotations, write out a 0-length annotations.
+  // XXX: Everything about HangAnnotations is awful.
+  if (!aParam.mAnnotations) {
+    WriteParam(aMsg, (size_t) 0);
+  } else {
     size_t length = aParam.mAnnotations->Count();
     WriteParam(aMsg, length);
     auto enumerator = aParam.mAnnotations->GetEnumerator();
-    nsAutoString key;
-    nsAutoString value;
-    while (enumerator->Next(key, value)) {
-      WriteParam(aMsg, key);
-      WriteParam(aMsg, value);
+    if (enumerator) {
+      nsAutoString key;
+      nsAutoString value;
+      while (enumerator->Next(key, value)) {
+        WriteParam(aMsg, key);
+        WriteParam(aMsg, value);
+      }
     }
   }