--- a/docshell/base/timeline/TimelineConsumers.cpp
+++ b/docshell/base/timeline/TimelineConsumers.cpp
@@ -2,16 +2,17 @@
 /* vim: set ts=8 sts=2 et sw=2 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 "TimelineConsumers.h"
 
 #include "mozilla/ClearOnShutdown.h"
+#include "jsapi.h"
 #include "nsAppRunner.h" // for XRE_IsContentProcess, XRE_IsParentProcess
 #include "nsDocShell.h"
 
 namespace mozilla {
 
 NS_IMPL_ISUPPORTS(TimelineConsumers, nsIObserver);
 
 StaticMutex TimelineConsumers::sMutex;
@@ -121,16 +122,19 @@ void
 TimelineConsumers::AddConsumer(nsDocShell* aDocShell)
 {
   MOZ_ASSERT(NS_IsMainThread());
   StaticMutexAutoLock lock(sMutex); // for `mActiveConsumers` and `mMarkersStores`.
 
   UniquePtr<ObservedDocShell>& observed = aDocShell->mObserved;
   MOZ_ASSERT(!observed);
 
+  if (mActiveConsumers == 0) {
+    JS::SetProfileTimelineRecordingEnabled(true);
+  }
   mActiveConsumers++;
 
   ObservedDocShell* obsDocShell = new ObservedDocShell(aDocShell);
   MarkersStorage* storage = static_cast<MarkersStorage*>(obsDocShell);
 
   observed.reset(obsDocShell);
   mMarkersStores.insertFront(storage);
 }
@@ -140,16 +144,19 @@ TimelineConsumers::RemoveConsumer(nsDocS
 {
   MOZ_ASSERT(NS_IsMainThread());
   StaticMutexAutoLock lock(sMutex); // for `mActiveConsumers` and `mMarkersStores`.
 
   UniquePtr<ObservedDocShell>& observed = aDocShell->mObserved;
   MOZ_ASSERT(observed);
 
   mActiveConsumers--;
+  if (mActiveConsumers == 0) {
+    JS::SetProfileTimelineRecordingEnabled(false);
+  }
 
   // Clear all markers from the `mTimelineMarkers` store.
   observed.get()->ClearMarkers();
   // Remove self from the `mMarkersStores` store.
   observed.get()->remove();
   // Prepare for becoming a consumer later.
   observed.reset(nullptr);
 }

--- a/js/src/jsapi.cpp
+++ b/js/src/jsapi.cpp
@@ -1334,16 +1334,30 @@ JS::detail::ComputeThis(JSContext* cx, V
     MutableHandleValue thisv = MutableHandleValue::fromMarkedLocation(&vp[1]);
     if (!BoxNonStrictThis(cx, thisv, thisv))
         return false;
 
     thisObject.set(&thisv.toObject());
     return true;
 }
 
+static bool gProfileTimelineRecordingEnabled = false;
+
+JS_PUBLIC_API(void)
+JS::SetProfileTimelineRecordingEnabled(bool enabled)
+{
+    gProfileTimelineRecordingEnabled = enabled;
+}
+
+JS_PUBLIC_API(bool)
+JS::IsProfileTimelineRecordingEnabled()
+{
+    return gProfileTimelineRecordingEnabled;
+}
+
 JS_PUBLIC_API(void*)
 JS_malloc(JSContext* cx, size_t nbytes)
 {
     AssertHeapIsIdle();
     CHECK_REQUEST(cx);
     return static_cast<void*>(cx->zone()->pod_malloc<uint8_t>(nbytes));
 }
 

--- a/js/src/jsapi.h
+++ b/js/src/jsapi.h
@@ -1497,16 +1497,32 @@ JS_InitReflectParse(JSContext* cx, JS::H
  */
 extern JS_PUBLIC_API(bool)
 JS_DefineProfilingFunctions(JSContext* cx, JS::HandleObject obj);
 
 /* Defined in vm/Debugger.cpp. */
 extern JS_PUBLIC_API(bool)
 JS_DefineDebuggerObject(JSContext* cx, JS::HandleObject obj);
 
+namespace JS {
+
+/**
+ * Tell JS engine whether Profile Timeline Recording is enabled or not.
+ * If Profile Timeline Recording is enabled, data shown there like stack won't
+ * be optimized out.
+ * This is global state and not associated with specific runtime or context.
+ */
+extern JS_PUBLIC_API(void)
+SetProfileTimelineRecordingEnabled(bool enabled);
+
+extern JS_PUBLIC_API(bool)
+IsProfileTimelineRecordingEnabled();
+
+} // namespace JS
+
 #ifdef JS_HAS_CTYPES
 /**
  * Initialize the 'ctypes' object on a global variable 'obj'. The 'ctypes'
  * object will be sealed.
  */
 extern JS_PUBLIC_API(bool)
 JS_InitCTypesClass(JSContext* cx, JS::HandleObject global);