--- a/js/src/jsapi.h
+++ b/js/src/jsapi.h
@@ -2211,17 +2211,18 @@ class JS_PUBLIC_API(CompartmentCreationO
     CompartmentCreationOptions()
       : addonId_(nullptr),
         traceGlobal_(nullptr),
         invisibleToDebugger_(false),
         mergeable_(false),
         preserveJitCode_(false),
         cloneSingletons_(false),
         experimentalDateTimeFormatFormatToPartsEnabled_(false),
-        sharedMemoryAndAtomics_(false)
+        sharedMemoryAndAtomics_(false),
+        secureContext_(false)
     {
         zone_.spec = JS::FreshZone;
     }
 
     // A null add-on ID means that the compartment is not associated with an
     // add-on.
     JSAddonId* addonIdOrNull() const { return addonId_; }
     CompartmentCreationOptions& setAddonId(JSAddonId* id) {
@@ -2294,29 +2295,40 @@ class JS_PUBLIC_API(CompartmentCreationO
     CompartmentCreationOptions& setExperimentalDateTimeFormatFormatToPartsEnabled(bool flag) {
         experimentalDateTimeFormatFormatToPartsEnabled_ = flag;
         return *this;
     }
 
     bool getSharedMemoryAndAtomicsEnabled() const;
     CompartmentCreationOptions& setSharedMemoryAndAtomicsEnabled(bool flag);
 
+    // This flag doesn't affect JS engine behavior.  It is used by Gecko to
+    // mark whether content windows and workers are "Secure Context"s. See
+    // https://w3c.github.io/webappsec-secure-contexts/
+    // https://bugzilla.mozilla.org/show_bug.cgi?id=1162772#c34
+    bool secureContext() const { return secureContext_; }
+    CompartmentCreationOptions& setSecureContext(bool flag) {
+        secureContext_ = flag;
+        return *this;
+    }
+
   private:
     JSAddonId* addonId_;
     JSTraceOp traceGlobal_;
     union {
         ZoneSpecifier spec;
         void* pointer; // js::Zone* is not exposed in the API.
     } zone_;
     bool invisibleToDebugger_;
     bool mergeable_;
     bool preserveJitCode_;
     bool cloneSingletons_;
     bool experimentalDateTimeFormatFormatToPartsEnabled_;
     bool sharedMemoryAndAtomics_;
+    bool secureContext_;
 };
 
 /**
  * CompartmentBehaviors specifies behaviors of a compartment that can be
  * changed after the compartment's been created.
  */
 class JS_PUBLIC_API(CompartmentBehaviors)
 {

--- a/js/src/jsfriendapi.cpp
+++ b/js/src/jsfriendapi.cpp
@@ -138,16 +138,22 @@ JS_NewObjectWithUniqueType(JSContext* cx
 
 JS_FRIEND_API(JSObject*)
 JS_NewObjectWithoutMetadata(JSContext* cx, const JSClass* clasp, JS::Handle<JSObject*> proto)
 {
     AutoSuppressAllocationMetadataBuilder suppressMetadata(cx);
     return JS_NewObjectWithGivenProto(cx, clasp, proto);
 }
 
+JS_FRIEND_API(bool)
+JS_GetIsSecureContext(JSCompartment* compartment)
+{
+    return compartment->creationOptions().secureContext();
+}
+
 JS_FRIEND_API(JSPrincipals*)
 JS_GetCompartmentPrincipals(JSCompartment* compartment)
 {
     return compartment->principals();
 }
 
 JS_FRIEND_API(void)
 JS_SetCompartmentPrincipals(JSCompartment* compartment, JSPrincipals* principals)

--- a/js/src/jsfriendapi.h
+++ b/js/src/jsfriendapi.h
@@ -142,16 +142,19 @@ static_assert(JS_TELEMETRY_DEFINE_GETTER
               "This value needs to be kept in sync with SelfHostingDefines.h");
 
 typedef void
 (*JSAccumulateTelemetryDataCallback)(int id, uint32_t sample, const char* key);
 
 extern JS_FRIEND_API(void)
 JS_SetAccumulateTelemetryCallback(JSRuntime* rt, JSAccumulateTelemetryDataCallback callback);
 
+extern JS_FRIEND_API(bool)
+JS_GetIsSecureContext(JSCompartment* compartment);
+
 extern JS_FRIEND_API(JSPrincipals*)
 JS_GetCompartmentPrincipals(JSCompartment* compartment);
 
 extern JS_FRIEND_API(void)
 JS_SetCompartmentPrincipals(JSCompartment* compartment, JSPrincipals* principals);
 
 extern JS_FRIEND_API(JSPrincipals*)
 JS_GetScriptPrincipals(JSScript* script);