Remove requirement that inline XRWebGLLayers use XR compatible contexts

This was a recent change made to the WebXR spec.

Bug: 976070
Change-Id: Ibdf4e4d7648d14540280594d7079696223a8dc62
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1728479Reviewed-by: Brian Sheedy <bsheedy@chromium.org>
Reviewed-by: Klaus Weidner <klausw@chromium.org>
Commit-Queue: Brandon Jones <bajones@chromium.org>
Cr-Commit-Position: refs/heads/master@{#683014}

third_party/blink/renderer/modules/xr/xr_webgl_layer.cc

@@ -57,10 +57,11 @@ XRWebGLLayer* XRWebGLLayer::Create(
     return nullptr;
   }
 
-  if (!webgl_context->IsXRCompatible()) {
+  if (session->immersive() && !webgl_context->IsXRCompatible()) {
     exception_state.ThrowDOMException(
         DOMExceptionCode::kInvalidStateError,
-        "This context is not marked as XR compatible.");
+        "WebGL context must be marked as XR compatible in order to "
+        "use with an immersive XRSession");
     return nullptr;
   }
 

third_party/blink/web_tests/external/wpt/webxr/xrWebGLLayer_constructor.https.html

@@ -16,7 +16,17 @@ xr_promise_test("Ensure that XRWebGLLayer's constructor throws appropriate error
   };
   let gl = webglCanvas.getContext('webgl', glAttributes);
   return navigator.xr.test.simulateDeviceConnection(TRACKED_IMMERSIVE_DEVICE)
-    .then((controller) => {
+    .then(() => {
+      return navigator.xr.requestSession('inline')
+        .then((session) => {
+          try {
+            let webglLayerIncompatible = new XRWebGLLayer(session, gl);
+          } catch (err) {
+            assert_unreached("Inline XRWebGLLayers should not fail when created with a context that is not XRCompatible");
+          }
+        });
+    })
+    .then(() => {
       return new Promise((resolve) => {
         navigator.xr.test.simulateUserActivation(() => {
           navigator.xr.requestSession('immersive-vr')