compute pressure: Adding WebIDL interface test

Introducing testing for WebIDL interface.

The method requestPermission() is not yet implemented, therefore
we need to add an "expected" file, because testing this method will
fail.

Bug: 1368452
Change-Id: Ib834996916a0d66cc98f5216b5eeca3dc261040a
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/3919091
Commit-Queue: Arnaud Mandy <arnaud.mandy@intel.com>
Reviewed-by: Fr <beaufort.francois@gmail.com>
Reviewed-by: Raphael Kubo Da Costa <raphael.kubo.da.costa@intel.com>
Cr-Commit-Position: refs/heads/main@{#1053497}
diff --git a/compute-pressure/idlharness.https.window.js b/compute-pressure/idlharness.https.window.js
new file mode 100644
index 0000000..1cdfb59
--- /dev/null
+++ b/compute-pressure/idlharness.https.window.js
@@ -0,0 +1,14 @@
+// META: script=/resources/WebIDLParser.js
+// META: script=/resources/idlharness.js
+
+// https://wicg.github.io/compute-pressure/
+
+'use strict';
+
+idl_test(['compute-pressure'], ['dom', 'html'], async idl_array => {
+  idl_array.add_objects({
+    PressureObserver: ['observer'],
+  });
+
+  self.observer = new PressureObserver(() => {}, {sampleRate: 1.0});
+});