Expose XRWebGLBinding interface

The XRWebGLBinding is defined in the WebXR Layers spec
(https://immersive-web.github.io/layers/); however, it is also required
by both the Lighting Estimation and Raw Camera Access specs.

We are not actively working on the layers spec; however, we want to
Origin Trial both Lighting Estimationa nd Raw Camera Access. This change
simplifies these cross-spec dependencies by shipping the empty
XRWebGLBinding interface.

I2S:
https://groups.google.com/u/1/a/chromium.org/g/blink-dev/c/6J0yfRuMmSU

Bug: 1070819
Change-Id: I8626fa854d892171542cec06a0befac76187fd84
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2519938
Commit-Queue: Alexander Cooper <alcooper@chromium.org>
Reviewed-by: Brandon Jones <bajones@chromium.org>
Reviewed-by: Yoav Weiss <yoavweiss@chromium.org>
Cr-Commit-Position: refs/heads/master@{#827380}

third_party/blink/renderer/modules/xr/xr_webgl_binding.idl

@@ -5,8 +5,7 @@
 // https://immersive-web.github.io/layers/#XRWebGLBindingtype
 [
     SecureContext,
-    Exposed=Window,
-    RuntimeEnabled=WebXRLightEstimation
+    Exposed=Window
 ] interface XRWebGLBinding {
   [RaisesException] constructor(XRSession session, XRWebGLRenderingContext context);
 

third_party/blink/web_tests/virtual/stable/webexposed/global-interface-listing-expected.txt

@@ -9326,6 +9326,9 @@ interface XRViewport
     getter x
     getter y
     method constructor
+interface XRWebGLBinding
+    attribute @@toStringTag
+    method constructor
 interface XRWebGLLayer : XRLayer
     static method getNativeFramebufferScaleFactor
     attribute @@toStringTag