Merge pull request #5431 from TrevorDev/xrErrorWarnings

add exceptions/warning to xr classes

src/Cameras/XR/babylon.webXRExperienceHelper.ts

@@ -101,6 +101,9 @@ module BABYLON {
          * @returns promise that resolves after xr mode has entered
          */
         public enterXRAsync(sessionCreationOptions: XRSessionCreationOptions, frameOfReference: string) {
+            if (!this._supported) {
+                throw "XR session not supported by this browser";
+            }
             this._setState(WebXRState.ENTERING_XR);
 
             return this._sessionManager.enterXRAsync(sessionCreationOptions, frameOfReference).then(() => {

src/Cameras/XR/babylon.webXRSessionManager.ts

@@ -39,7 +39,8 @@ module BABYLON {
          * @returns Promise which resolves after it is initialized
          */
         public initializeAsync(): Promise<void> {
-             // Check if the browser supports webXR
+            Tools.Warn("The WebXR APIs are still under development and are subject to change in the future.");
+            // Check if the browser supports webXR
             this._xrNavigator = navigator;
             if (!this._xrNavigator.xr) {
                 return Promise.reject("webXR not supported by this browser");