Move "SanitizerAPI" back to experimental.

When we shipped Sanitizer API, we split the flag into "SanitizerAPIv0"
(which was promoted to stable and then removed), and reserved the
"SanitizerAPI" for future enhancements. Since we're now removing the API
from stable, we'll gate it on the "SanitizerAPI" flag (instead of re-
introducing the "...v0" variant).

Intent-to-remove here: https://groups.google.com/a/chromium.org/g/blink-dev/c/PNTt4oFXt8c

Bug: 1428276
Change-Id: I79b18184f1a44a85c3eb3b1cfc38b2e54f728e5c
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/4894112
Reviewed-by: Yoav Weiss <yoavweiss@chromium.org>
Reviewed-by: Yifan Luo <lyf@chromium.org>
Commit-Queue: Daniel Vogelheim <vogelheim@chromium.org>
Cr-Commit-Position: refs/heads/main@{#1202557}

third_party/blink/renderer/modules/sanitizer_api/README.md

@@ -24,13 +24,15 @@ go to https://bugs.chromium.org and use the
 
 ## Staged / Incremental Rollout
 
-An initial version of the Sanitizer API is enabled by default. Additional
-features are scheduled to be launched in stages. The API availability
+The Sanitizer API is scheduled to be launched in stages. The API availability
 can be controlled via flags:
 
-* `--enable-blink-features=SanitizerAPI`: This includes the sanitization
-  methods of the `Sanitizer` object, as specified as of 04/2022.
-These APIs are likely to change.
+* `--enable-blink-features=SanitizerAPIv0`: This includes the basic Sanitizer
+  API with configuration and the `Element.setHTML` method, but not the
+  `.sanitizeFor` or `.sanitize` methods. This flag is on by default.
+* `--enable-blink-features=SanitizerAPI`: This includes `SanitizerAPv0`
+  plus the sanitization methods of the `Sanitizer` object, as specified
+  as of 04/2022. These APIs are likely to change.
 
 The general `--enable-experimental-web-platform-features` flag implies the full
 `--enable-blink-features=SanitizerAPI` feature set.

third_party/blink/renderer/modules/sanitizer_api/element_sanitizer.idl

@@ -9,6 +9,7 @@ dictionary ElementSetHTMLOptions {
 };
 
 [
+  RuntimeEnabled=SanitizerAPI,
   SecureContext,
   ImplementedAs=ElementSanitizer
 ] partial interface Element {

third_party/blink/renderer/modules/sanitizer_api/sanitizer.idl

@@ -8,13 +8,14 @@ typedef (DocumentFragment or Document) SanitizerInput;
 
 [
   Exposed=Window,
-  SecureContext
+  SecureContext,
+  RuntimeEnabled=SanitizerAPI
 ] interface Sanitizer {
   [MeasureAs=SanitizerAPICreated, CallWith=ExecutionContext, RaisesException] constructor(optional SanitizerConfig config = {});
 
-  [MeasureAs=SanitizerAPIToFragment, RuntimeEnabled=SanitizerAPI,
+  [MeasureAs=SanitizerAPIToFragment,
 CallWith=ScriptState, RaisesException] DocumentFragment sanitize(SanitizerInput input);
-  [MeasureAs=SanitizerAPISanitizeFor, RuntimeEnabled=SanitizerAPI, CallWith=ScriptState, RaisesException] Element? sanitizeFor(DOMString element, DOMString markup);
+  [MeasureAs=SanitizerAPISanitizeFor, CallWith=ScriptState, RaisesException] Element? sanitizeFor(DOMString element, DOMString markup);
 
   [MeasureAs=SanitizerAPIGetConfig] SanitizerConfig getConfiguration();
   [MeasureAs=SanitizerAPIGetDefaultConfig] static SanitizerConfig getDefaultConfiguration();

third_party/blink/web_tests/virtual/stable/webexposed/element-instance-property-listing-expected.txt

@@ -309,7 +309,6 @@ namespace http://www.w3.org/1999/xhtml
     property setAttributeNS
     property setAttributeNode
     property setAttributeNodeNS
-    property setHTML
     property setPointerCapture
     property shadowRoot
     property showPopover
@@ -1494,7 +1493,6 @@ namespace http://www.w3.org/2000/svg
     property setAttributeNS
     property setAttributeNode
     property setAttributeNodeNS
-    property setHTML
     property setPointerCapture
     property shadowRoot
     property slot

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

@@ -1978,7 +1978,6 @@ interface Element : Node
     method setAttributeNS
     method setAttributeNode
     method setAttributeNodeNS
-    method setHTML
     method setPointerCapture
     method toggleAttribute
     method webkitMatchesSelector
@@ -8039,11 +8038,6 @@ interface SVGViewElement : SVGElement
     getter zoomAndPan
     method constructor
     setter zoomAndPan
-interface Sanitizer
-    static method getDefaultConfiguration
-    attribute @@toStringTag
-    method constructor
-    method getConfiguration
 interface Scheduler
     attribute @@toStringTag
     method constructor