Replace asynchronous .requestAdapterInfo() with synchronous .info (gp…

…uweb#4662)

Replaces the GPUAdapter method
`Promise<GPUAdapterInfo> requestAdapterInfo();`
with a synchronous attribute
`[SameObject] readonly attribute GPUAdapterInfo info;`

Important points:

- `requestAdapterInfo()` is removed. Chromium will deprecate and remove it and attempt to get any sites migrated off of it, so hopefully Firefox/Safari won't have to implement it at all (though the implementation is trivial so they may choose to, for compatibility with outdated sites).
- The available info about a given `GPUAdapter` may no longer change. You can only get new info by getting a new `GPUAdapter`. (The only reason this should happen is if someone adds a permission prompt for fingerprintability.)

Less important points:
- You can now only get one `GPUAdapterInfo` object per `GPUAdapter` object, since `adapter.info` returns the same object every time you access it.

design/AdapterIdentifiers.md

@@ -1,5 +1,10 @@
 # WebGPU Adapter Identifiers
 
+**This document is outdated. `adapter.requestAdapterInfo()` has been replaced with
+`adapter.info` and `unmaskHints` doesn't exist anymore. See:
+[#4536](https://github.com/gpuweb/gpuweb/issues/4536),
+[#4316](https://github.com/gpuweb/gpuweb/pull/4316).
+
 ## Introduction
 
 The WebGL extension [WEBGL_debug_renderer_info](https://www.khronos.org/registry/webgl/extensions/WEBGL_debug_renderer_info/) reports identifying information about a device's graphics driver for the purposes of debugging or detection and avoidance of bugs or performance pitfalls on a particular driver or piece of hardware.

spec/index.bs

@@ -737,7 +737,6 @@ Several operations in WebGPU return promises.
 
 - {{GPU}}.{{GPU/requestAdapter()}}
 - {{GPUAdapter}}.{{GPUAdapter/requestDevice()}}
-- {{GPUAdapter}}.{{GPUAdapter/requestAdapterInfo()}}
 - {{GPUDevice}}.{{GPUDevice/createComputePipelineAsync()}}
 - {{GPUDevice}}.{{GPUDevice/createRenderPipelineAsync()}}
 - {{GPUBuffer}}.{{GPUBuffer/mapAsync()}}
@@ -1699,11 +1698,26 @@ interface WGSLLanguageFeatures {
 
 {{GPUAdapterInfo}} exposes various identifying information about an adapter.
 
-None of the members in {{GPUAdapterInfo}} are guaranteed to be populated. It is at the user
+None of the members in {{GPUAdapterInfo}} are guaranteed to be populated with any particular value;
+if no value is provided, the attribute will return the empty string `""`. It is at the user
 agent's discretion which values to reveal, and it is likely that on some devices none of the values
 will be populated. As such, applications **must** be able to handle any possible {{GPUAdapterInfo}} values,
 including the absence of those values.
 
+The information exposed by a {{GPUAdapter}} is immutable: for a given adapter, each {{GPUAdapterInfo}}
+attribute will return the same value every time it's accessed.
+
+Note:
+Though the {{GPUAdapterInfo}} attributes are immutable *once accessed*, an implementation may delay the decision on
+what to expose for each attribute until the first time it is accessed.
+
+Note:
+Other {{GPUAdapter}} instances, even if they represent the same physical adapter, may expose
+different values in {{GPUAdapterInfo}}.
+However, they **should** expose the same values unless a specific
+event has increased the amount of identifying information the page is allowed to access.
+(No such events are defined by this specification.)
+
 <p tracking-vector>
 For privacy considerations, see [[#privacy-adapter-identifiers]].
 </p>
@@ -2337,10 +2351,10 @@ To get a {{GPUAdapter}}, use {{GPU/requestAdapter()}}.
 interface GPUAdapter {
     [SameObject] readonly attribute GPUSupportedFeatures features;
     [SameObject] readonly attribute GPUSupportedLimits limits;
+    [SameObject] readonly attribute GPUAdapterInfo info;
     readonly attribute boolean isFallbackAdapter;
 
     Promise<GPUDevice> requestDevice(optional GPUDeviceDescriptor descriptor = {});
-    Promise<GPUAdapterInfo> requestAdapterInfo();
 };
 </script>
 
@@ -2355,6 +2369,26 @@ interface GPUAdapter {
     ::
         The limits in `this`.{{GPUAdapter/[[adapter]]}}.{{adapter/[[limits]]}}.
 
+    : <dfn>info</dfn>
+    ::
+        Information about the physical adapter underlying this {{GPUAdapter}}.
+
+        For a given {{GPUAdapter}}, the {{GPUAdapterInfo}} values exposed are constant over time.
+
+        The same object is returned each time. To create that object for the first time:
+
+        <div algorithm=GPUAdapter.info>
+            <div data-timeline=content>
+                **Called on:** {{GPUAdapter}} |this|.
+
+                **Returns:** {{GPUAdapterInfo}}
+
+                [=Content timeline=] steps:
+
+                1. Return a [$new adapter info$] for |this|.{{GPUAdapter/[[adapter]]}}.
+            </div>
+        </div>
+
     : <dfn>isFallbackAdapter</dfn>
     ::
         Returns the value of {{GPUAdapter/[[adapter]]}}.{{adapter/[[fallback]]}}.
@@ -2476,30 +2510,6 @@ interface GPUAdapter {
                     |device|.{{GPUDevice/lost}} has already resolved before |promise| resolves.
             </div>
         </div>
-
-    : <dfn>requestAdapterInfo()</dfn>
-    ::
-        Requests the {{GPUAdapterInfo}} for this {{GPUAdapter}}.
-
-        Note: Adapter info values are returned with a Promise to give user agents an
-        opportunity to perform potentially long-running checks in the future.
-
-        <div algorithm=GPUAdapter.requestAdapterInfo>
-            <div data-timeline=content>
-                **Called on:** {{GPUAdapter}} |this|.
-
-                **Returns:** {{Promise}}&lt;{{GPUAdapterInfo}}&gt;
-
-                [=Content timeline=] steps:
-
-                1. Let |promise| be [=a new promise=].
-                1. Let |adapter| be |this|.{{GPUAdapter/[[adapter]]}}.
-                1. Run the following steps [=in parallel=]:
-                    1. [=Resolve=] |promise| with a [$new adapter info$] for |adapter|.
-
-                1. Return |promise|.
-            </div>
-        </div>
 </dl>
 
 <div class=example>