--- a/dom/base/nsGlobalWindow.cpp
+++ b/dom/base/nsGlobalWindow.cpp
@@ -1434,16 +1434,18 @@ nsGlobalWindow::DropOuterWindowDocs()
 void
 nsGlobalWindow::CleanUp()
 {
   // Guarantee idempotence.
   if (mCleanedUp)
     return;
   mCleanedUp = true;
 
+  StartDying();
+
   mEventTargetObjects.EnumerateEntries(DisconnectEventTargetObjects, nullptr);
   mEventTargetObjects.Clear();
 
   if (mObserver) {
     nsCOMPtr<nsIObserverService> os = mozilla::services::GetObserverService();
     if (os) {
       os->RemoveObserver(mObserver, NS_IOSERVICE_OFFLINE_STATUS_TOPIC);
       os->RemoveObserver(mObserver, "dom-storage2-changed");

--- a/dom/base/nsIGlobalObject.h
+++ b/dom/base/nsIGlobalObject.h
@@ -12,21 +12,55 @@
 #define NS_IGLOBALOBJECT_IID \
 { 0xe2538ded, 0x13ef, 0x4f4d, \
 { 0x94, 0x6b, 0x65, 0xd3, 0x33, 0xb4, 0xf0, 0x3c } }
 
 class nsIPrincipal;
 
 class nsIGlobalObject : public nsISupports
 {
+  bool mIsDying;
+
+protected:
+  nsIGlobalObject()
+   : mIsDying(false)
+  {}
+
 public:
   NS_DECLARE_STATIC_IID_ACCESSOR(NS_IGLOBALOBJECT_IID)
 
+  /**
+   * This check is added to deal with Promise microtask queues. On the main
+   * thread, we do not impose restrictions about when script stops running or
+   * when runnables can no longer be dispatched to the main thread. This means
+   * it is possible for a Promise chain to keep resolving an infinite chain of
+   * promises, preventing the browser from shutting down. See Bug 1058695. To
+   * prevent this, the nsGlobalWindow subclass sets this flag when it is
+   * closed. The Promise implementation checks this and prohibits new runnables
+   * from being dispatched.
+   *
+   * We pair this with checks during processing the promise microtask queue
+   * that pops up the slow script dialog when the Promise queue is preventing
+   * a window from going away.
+   */
+  bool
+  IsDying() const
+  {
+    return mIsDying;
+  }
+
   virtual JSObject* GetGlobalJSObject() = 0;
 
   // This method is not meant to be overridden.
   nsIPrincipal* PrincipalOrNull();
+
+protected:
+  void
+  StartDying()
+  {
+    mIsDying = true;
+  }
 };
 
 NS_DEFINE_STATIC_IID_ACCESSOR(nsIGlobalObject,
                               NS_IGLOBALOBJECT_IID)
 
 #endif // nsIGlobalObject_h__

--- a/dom/promise/Promise.cpp
+++ b/dom/promise/Promise.cpp
@@ -258,17 +258,17 @@ protected:
 
         mPromise->RejectInternal(cx, exn);
       }
       // At least one of resolveFunc or rejectFunc have been called, so ignore
       // the exception. FIXME(nsm): This should be reported to the error
       // console though, for debugging.
     }
 
-    return NS_OK;
+    return rv.StealNSResult();
   }
 
 private:
   nsRefPtr<Promise> mPromise;
   JS::PersistentRooted<JSObject*> mThenable;
   nsRefPtr<PromiseInit> mThen;
   NS_DECL_OWNINGTHREAD;
 };
@@ -484,23 +484,34 @@ Promise::PerformMicroTaskCheckpoint()
   CycleCollectedJSRuntime* runtime = CycleCollectedJSRuntime::Get();
   nsTArray<nsCOMPtr<nsIRunnable>>& microtaskQueue =
     runtime->GetPromiseMicroTaskQueue();
 
   if (microtaskQueue.IsEmpty()) {
     return false;
   }
 
+  Maybe<AutoSafeJSContext> cx;
+  if (NS_IsMainThread()) {
+    cx.emplace();
+  }
+
   do {
     nsCOMPtr<nsIRunnable> runnable = microtaskQueue.ElementAt(0);
     MOZ_ASSERT(runnable);
 
     // This function can re-enter, so we remove the element before calling.
     microtaskQueue.RemoveElementAt(0);
-    runnable->Run();
+    nsresult rv = runnable->Run();
+    if (NS_WARN_IF(NS_FAILED(rv))) {
+      return false;
+    }
+    if (cx.isSome()) {
+      JS_CheckForInterrupt(cx.ref());
+    }
   } while (!microtaskQueue.IsEmpty());
 
   return true;
 }
 
 /* static */ bool
 Promise::JSCallback(JSContext* aCx, unsigned aArgc, JS::Value* aVp)
 {
@@ -1066,16 +1077,20 @@ Promise::Compartment() const
 {
   return js::GetObjectCompartment(GlobalJSObject());
 }
 
 void
 Promise::AppendCallbacks(PromiseCallback* aResolveCallback,
                          PromiseCallback* aRejectCallback)
 {
+  if (mGlobal->IsDying()) {
+    return;
+  }
+
   MOZ_ASSERT(aResolveCallback);
   MOZ_ASSERT(aRejectCallback);
 
   if (mIsLastInChain && mState == PromiseState::Rejected) {
     // This rejection is now consumed.
     PromiseDebugging::AddConsumedRejection(*this);
     // Note that we may not have had the opportunity to call
     // RunResolveTask() yet, so we may never have called
@@ -1292,17 +1307,22 @@ Promise::RejectInternal(JSContext* aCx,
   mResolvePending = true;
 
   MaybeSettle(aValue, Rejected);
 }
 
 void
 Promise::Settle(JS::Handle<JS::Value> aValue, PromiseState aState)
 {
+  if (mGlobal->IsDying()) {
+    return;
+  }
+
   mSettlementTimestamp = TimeStamp::Now();
+
   SetResult(aValue);
   SetState(aState);
 
   AutoJSAPI jsapi;
   jsapi.Init();
   JSContext* cx = jsapi.cx();
   JS::RootedObject wrapper(cx, GetWrapper());
   MOZ_ASSERT(wrapper); // We preserved it

--- a/dom/promise/PromiseCallback.cpp
+++ b/dom/promise/PromiseCallback.cpp
@@ -66,30 +66,31 @@ ResolvePromiseCallback::ResolvePromiseCa
   HoldJSObjects(this);
 }
 
 ResolvePromiseCallback::~ResolvePromiseCallback()
 {
   DropJSObjects(this);
 }
 
-void
+nsresult
 ResolvePromiseCallback::Call(JSContext* aCx,
                              JS::Handle<JS::Value> aValue)
 {
   // Run resolver's algorithm with value and the synchronous flag set.
 
   JSAutoCompartment ac(aCx, mGlobal);
   JS::Rooted<JS::Value> value(aCx, aValue);
   if (!JS_WrapValue(aCx, &value)) {
     NS_WARNING("Failed to wrap value into the right compartment.");
-    return;
+    return NS_ERROR_FAILURE;
   }
 
   mPromise->ResolveInternal(aCx, value);
+  return NS_OK;
 }
 
 // RejectPromiseCallback
 
 NS_IMPL_CYCLE_COLLECTION_CLASS(RejectPromiseCallback)
 
 NS_IMPL_CYCLE_COLLECTION_UNLINK_BEGIN_INHERITED(RejectPromiseCallback,
                                                 PromiseCallback)
@@ -124,31 +125,32 @@ RejectPromiseCallback::RejectPromiseCall
   HoldJSObjects(this);
 }
 
 RejectPromiseCallback::~RejectPromiseCallback()
 {
   DropJSObjects(this);
 }
 
-void
+nsresult
 RejectPromiseCallback::Call(JSContext* aCx,
                             JS::Handle<JS::Value> aValue)
 {
   // Run resolver's algorithm with value and the synchronous flag set.
 
   JSAutoCompartment ac(aCx, mGlobal);
   JS::Rooted<JS::Value> value(aCx, aValue);
   if (!JS_WrapValue(aCx, &value)) {
     NS_WARNING("Failed to wrap value into the right compartment.");
-    return;
+    return NS_ERROR_FAILURE;
   }
 
 
   mPromise->RejectInternal(aCx, value);
+  return NS_OK;
 }
 
 // WrapperPromiseCallback
 NS_IMPL_CYCLE_COLLECTION_CLASS(WrapperPromiseCallback)
 
 NS_IMPL_CYCLE_COLLECTION_UNLINK_BEGIN_INHERITED(WrapperPromiseCallback,
                                                 PromiseCallback)
   NS_IMPL_CYCLE_COLLECTION_UNLINK(mNextPromise)
@@ -185,25 +187,25 @@ WrapperPromiseCallback::WrapperPromiseCa
   HoldJSObjects(this);
 }
 
 WrapperPromiseCallback::~WrapperPromiseCallback()
 {
   DropJSObjects(this);
 }
 
-void
+nsresult
 WrapperPromiseCallback::Call(JSContext* aCx,
                              JS::Handle<JS::Value> aValue)
 {
   JSAutoCompartment ac(aCx, mGlobal);
   JS::Rooted<JS::Value> value(aCx, aValue);
   if (!JS_WrapValue(aCx, &value)) {
     NS_WARNING("Failed to wrap value into the right compartment.");
-    return;
+    return NS_ERROR_FAILURE;
   }
 
   ErrorResult rv;
 
   // PromiseReactionTask step 6
   JS::Rooted<JS::Value> retValue(aCx);
   mCallback->Call(value, &retValue, rv, "promise callback",
                   CallbackObject::eRethrowExceptions,
@@ -214,30 +216,30 @@ WrapperPromiseCallback::Call(JSContext* 
   // PromiseReactionTask step 7
   if (rv.Failed()) {
     JS::Rooted<JS::Value> value(aCx);
     if (rv.IsJSException()) {
       rv.StealJSException(aCx, &value);
 
       if (!JS_WrapValue(aCx, &value)) {
         NS_WARNING("Failed to wrap value into the right compartment.");
-        return;
+        return NS_ERROR_FAILURE;
       }
     } else {
       // Convert the ErrorResult to a JS exception object that we can reject
       // ourselves with.  This will be exactly the exception that would get
       // thrown from a binding method whose ErrorResult ended up with whatever
       // is on "rv" right now.
       JSAutoCompartment ac(aCx, mNextPromise->GlobalJSObject());
       DebugOnly<bool> conversionResult = ToJSValue(aCx, rv, &value);
       MOZ_ASSERT(conversionResult);
     }
 
     mNextPromise->RejectInternal(aCx, value);
-    return;
+    return NS_OK;
   }
 
   // If the return value is the same as the promise itself, throw TypeError.
   if (retValue.isObject()) {
     JS::Rooted<JSObject*> valueObj(aCx, &retValue.toObject());
     Promise* returnedPromise;
     nsresult r = UNWRAP_OBJECT(Promise, valueObj, returnedPromise);
 
@@ -265,48 +267,49 @@ WrapperPromiseCallback::Call(JSContext* 
         }
       }
 
       // We're back in aValue's compartment here.
       JS::Rooted<JSString*> fn(aCx, JS_NewStringCopyZ(aCx, fileName));
       if (!fn) {
         // Out of memory. Promise will stay unresolved.
         JS_ClearPendingException(aCx);
-        return;
+        return NS_ERROR_OUT_OF_MEMORY;
       }
 
       JS::Rooted<JSString*> message(aCx,
         JS_NewStringCopyZ(aCx,
           "then() cannot return same Promise that it resolves."));
       if (!message) {
         // Out of memory. Promise will stay unresolved.
         JS_ClearPendingException(aCx);
-        return;
+        return NS_ERROR_OUT_OF_MEMORY;
       }
 
       JS::Rooted<JS::Value> typeError(aCx);
       if (!JS::CreateError(aCx, JSEXN_TYPEERR, JS::NullPtr(), fn, lineNumber, 0,
                            nullptr, message, &typeError)) {
         // Out of memory. Promise will stay unresolved.
         JS_ClearPendingException(aCx);
-        return;
+        return NS_ERROR_OUT_OF_MEMORY;
       }
 
       mNextPromise->RejectInternal(aCx, typeError);
-      return;
+      return NS_OK;
     }
   }
 
   // Otherwise, run resolver's resolve with value.
   if (!JS_WrapValue(aCx, &retValue)) {
     NS_WARNING("Failed to wrap value into the right compartment.");
-    return;
+    return NS_ERROR_FAILURE;
   }
 
   mNextPromise->ResolveInternal(aCx, retValue);
+  return NS_OK;
 }
 
 // NativePromiseCallback
 
 NS_IMPL_CYCLE_COLLECTION_INHERITED(NativePromiseCallback,
                                    PromiseCallback, mHandler)
 
 NS_INTERFACE_MAP_BEGIN_CYCLE_COLLECTION_INHERITED(NativePromiseCallback)
@@ -322,31 +325,32 @@ NativePromiseCallback::NativePromiseCall
 {
   MOZ_ASSERT(aHandler);
 }
 
 NativePromiseCallback::~NativePromiseCallback()
 {
 }
 
-void
+nsresult
 NativePromiseCallback::Call(JSContext* aCx,
                             JS::Handle<JS::Value> aValue)
 {
   if (mState == Promise::Resolved) {
     mHandler->ResolvedCallback(aCx, aValue);
-    return;
+    return NS_OK;
   }
 
   if (mState == Promise::Rejected) {
     mHandler->RejectedCallback(aCx, aValue);
-    return;
+    return NS_OK;
   }
 
   NS_NOTREACHED("huh?");
+  return NS_ERROR_FAILURE;
 }
 
 /* static */ PromiseCallback*
 PromiseCallback::Factory(Promise* aNextPromise, JS::Handle<JSObject*> aGlobal,
                          AnyCallback* aCallback, Task aTask)
 {
   MOZ_ASSERT(aNextPromise);
 

--- a/dom/promise/PromiseCallback.h
+++ b/dom/promise/PromiseCallback.h
@@ -21,18 +21,18 @@ protected:
   virtual ~PromiseCallback();
 
 public:
   NS_DECL_CYCLE_COLLECTING_ISUPPORTS
   NS_DECL_CYCLE_COLLECTION_CLASS(PromiseCallback)
 
   PromiseCallback();
 
-  virtual void Call(JSContext* aCx,
-                    JS::Handle<JS::Value> aValue) = 0;
+  virtual nsresult Call(JSContext* aCx,
+                        JS::Handle<JS::Value> aValue) = 0;
 
   // Return the Promise that this callback will end up resolving or
   // rejecting, if any.
   virtual Promise* GetDependentPromise() = 0;
 
   enum Task {
     Resolve,
     Reject
@@ -49,18 +49,18 @@ public:
 // aNextPromise->RejectFunction() if the JS Callback throws.
 class WrapperPromiseCallback final : public PromiseCallback
 {
 public:
   NS_DECL_ISUPPORTS_INHERITED
   NS_DECL_CYCLE_COLLECTION_SCRIPT_HOLDER_CLASS_INHERITED(WrapperPromiseCallback,
                                                          PromiseCallback)
 
-  void Call(JSContext* aCx,
-            JS::Handle<JS::Value> aValue) override;
+  nsresult Call(JSContext* aCx,
+                JS::Handle<JS::Value> aValue) override;
 
   Promise* GetDependentPromise() override
   {
     return mNextPromise;
   }
 
   WrapperPromiseCallback(Promise* aNextPromise, JS::Handle<JSObject*> aGlobal,
                          AnyCallback* aCallback);
@@ -77,18 +77,18 @@ private:
 // received by Call().
 class ResolvePromiseCallback final : public PromiseCallback
 {
 public:
   NS_DECL_ISUPPORTS_INHERITED
   NS_DECL_CYCLE_COLLECTION_SCRIPT_HOLDER_CLASS_INHERITED(ResolvePromiseCallback,
                                                          PromiseCallback)
 
-  void Call(JSContext* aCx,
-            JS::Handle<JS::Value> aValue) override;
+  nsresult Call(JSContext* aCx,
+                JS::Handle<JS::Value> aValue) override;
 
   Promise* GetDependentPromise() override
   {
     return mPromise;
   }
 
   ResolvePromiseCallback(Promise* aPromise, JS::Handle<JSObject*> aGlobal);
 
@@ -103,18 +103,18 @@ private:
 // received by Call().
 class RejectPromiseCallback final : public PromiseCallback
 {
 public:
   NS_DECL_ISUPPORTS_INHERITED
   NS_DECL_CYCLE_COLLECTION_SCRIPT_HOLDER_CLASS_INHERITED(RejectPromiseCallback,
                                                          PromiseCallback)
 
-  void Call(JSContext* aCx,
-            JS::Handle<JS::Value> aValue) override;
+  nsresult Call(JSContext* aCx,
+                JS::Handle<JS::Value> aValue) override;
 
   Promise* GetDependentPromise() override
   {
     return mPromise;
   }
 
   RejectPromiseCallback(Promise* aPromise, JS::Handle<JSObject*> aGlobal);
 
@@ -128,18 +128,18 @@ private:
 // NativePromiseCallback wraps a PromiseNativeHandler.
 class NativePromiseCallback final : public PromiseCallback
 {
 public:
   NS_DECL_ISUPPORTS_INHERITED
   NS_DECL_CYCLE_COLLECTION_CLASS_INHERITED(NativePromiseCallback,
                                            PromiseCallback)
 
-  void Call(JSContext* aCx,
-            JS::Handle<JS::Value> aValue) override;
+  nsresult Call(JSContext* aCx,
+                JS::Handle<JS::Value> aValue) override;
 
   Promise* GetDependentPromise() override
   {
     return nullptr;
   }
 
   NativePromiseCallback(PromiseNativeHandler* aHandler,
                         Promise::PromiseState aState);

--- a/js/src/jsapi.cpp
+++ b/js/src/jsapi.cpp
@@ -4457,16 +4457,22 @@ JS_New(JSContext* cx, HandleObject ctor,
     RootedObject obj(cx);
     {
         AutoLastFrameCheck lfc(cx);
         obj = JS_NewHelper(cx, ctor, inputArgs);
     }
     return obj;
 }
 
+JS_PUBLIC_API(bool)
+JS_CheckForInterrupt(JSContext* cx)
+{
+    return js::CheckForInterrupt(cx);
+}
+
 JS_PUBLIC_API(JSInterruptCallback)
 JS_SetInterruptCallback(JSRuntime* rt, JSInterruptCallback callback)
 {
     JSInterruptCallback old = rt->interruptCallback;
     rt->interruptCallback = callback;
     return old;
 }
 

--- a/js/src/jsapi.h
+++ b/js/src/jsapi.h
@@ -3943,19 +3943,21 @@ Call(JSContext* cx, JS::HandleValue this
     JS::RootedValue fun(cx, JS::ObjectValue(*funObj));
     return Call(cx, thisv, fun, args, rval);
 }
 
 extern JS_PUBLIC_API(bool)
 Construct(JSContext* cx, JS::HandleValue fun,
           const JS::HandleValueArray& args,
           MutableHandleValue rval);
-
 } /* namespace JS */
 
+extern JS_PUBLIC_API(bool)
+JS_CheckForInterrupt(JSContext* cx);
+
 /*
  * These functions allow setting an interrupt callback that will be called
  * from the JS thread some time after any thread triggered the callback using
  * JS_RequestInterruptCallback(rt).
  *
  * To schedule the GC and for other activities the engine internally triggers
  * interrupt callbacks. The embedding should thus not rely on callbacks being
  * triggered through the external API only.

--- a/js/xpconnect/src/XPCJSRuntime.cpp
+++ b/js/xpconnect/src/XPCJSRuntime.cpp
@@ -1456,18 +1456,23 @@ XPCJSRuntime::InterruptCallback(JSContex
         if (!JS_GetPrototype(cx, global, &proto))
             return false;
         if (proto && IsSandboxPrototypeProxy(proto) &&
             (proto = js::CheckedUnwrap(proto, /* stopAtOuter = */ false)))
         {
             win = WindowGlobalOrNull(proto);
         }
     }
-    if (!win)
+
+    if (!win) {
+        NS_WARNING("No active window");
         return true;
+    }
+
+    MOZ_ASSERT(!win->IsDying());
 
     if (win->GetIsPrerendered()) {
         // We cannot display a dialog if the page is being prerendered, so
         // just kill the page.
         mozilla::dom::HandlePrerenderingViolation(win);
         return false;
     }