Update interfaces/webxr.idl (#15737)

Source: https://github.com/tidoust/reffy-reports/blob/4fe3242/whatwg/idl/webxr.idl
Build: https://travis-ci.org/tidoust/reffy-reports/builds/503472117
diff --git a/interfaces/webxr.idl b/interfaces/webxr.idl
index e91a50c..1bbe7ef 100644
--- a/interfaces/webxr.idl
+++ b/interfaces/webxr.idl
@@ -133,7 +133,6 @@
 [SecureContext, Exposed=Window] interface XRView {
   readonly attribute XREye eye;
   readonly attribute Float32Array projectionMatrix;
-  readonly attribute Float32Array viewMatrix;
   readonly attribute XRRigidTransform transform;
 };
 
@@ -150,6 +149,8 @@
   readonly attribute DOMPointReadOnly position;
   readonly attribute DOMPointReadOnly orientation;
   readonly attribute Float32Array matrix;
+
+  XRRigidTransform inverse();
 };
 
 [SecureContext, Exposed=Window,
@@ -200,6 +201,7 @@
   boolean depth = true;
   boolean stencil = false;
   boolean alpha = true;
+  boolean ignoreDepthValues = false;
   double framebufferScaleFactor = 1.0;
 };
 
@@ -214,6 +216,7 @@
   readonly attribute boolean depth;
   readonly attribute boolean stencil;
   readonly attribute boolean alpha;
+  readonly attribute boolean ignoreDepthValues;
 
   readonly attribute WebGLFramebuffer framebuffer;
   readonly attribute unsigned long framebufferWidth;