Bug 1439788 - Add performance.now() function to JS shell. r=arai

--HG--
extra : rebase_source : ac2642afd1fd76909d690b51eb62035c5d77ee92

js/src/shell/js.cpp

@@ -7457,6 +7457,14 @@ TestAssertRecoveredOnBailout,
     JS_FS_HELP_END
 };
 
+static const JSFunctionSpecWithHelp performance_functions[] = {
+    JS_FN_HELP("now", Now, 0, 0,
+"now()",
+"  Return the current time with sub-ms precision.\n"
+"  This function is an alias of the dateNow() function."),
+    JS_FS_HELP_END
+};
+
 static const JSFunctionSpecWithHelp console_functions[] = {
     JS_FN_HELP("log", Print, 0, 0,
 "log([exp ...])",
@@ -8385,6 +8393,8 @@ NewGlobalObject(JSContext* cx, JS::CompartmentOptions& options,
         RootedObject performanceObj(cx, JS_NewObject(cx, nullptr));
         if (!performanceObj)
             return nullptr;
+        if (!JS_DefineFunctionsWithHelp(cx, performanceObj, performance_functions))
+            return nullptr;
         RootedObject mozMemoryObj(cx, JS_NewObject(cx, nullptr));
         if (!mozMemoryObj)
             return nullptr;