dart:indexed_db: deprecate IdbFactory.supportsDatabaseNames

This has been removed from modern browsers - always returns false

See https://chromestatus.com/features/5725741740195840

Fixes https://github.com/dart-lang/sdk/issues/48047

Change-Id: Ie93757f664d892ba365a99c524a8ae79466e5002
Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/226180
Reviewed-by: Srujan Gaddam <srujzs@google.com>
Auto-Submit: Kevin Moore <kevmoo@google.com>
Commit-Queue: Kevin Moore <kevmoo@google.com>

CHANGELOG.md

@@ -12,6 +12,11 @@
   error with an existing stack trace, instead of creating
   a new stack trace.
 
+#### `dart:indexed_db`
+
+- `IdbFactory.supportsDatabaseNames` has been deprecated. It will always return
+  `false`.
+
 #### `dart:io`
 
 - **Breaking Change** [#47769](https://github.com/dart-lang/sdk/issues/47769):

sdk/lib/indexed_db/dart2js/indexed_db_dart2js.dart

@@ -507,14 +507,10 @@ class IdbFactory extends JavaScriptObject {
   }
 
   /**
-   * Checks to see if getDatabaseNames is supported by the current platform.
-   * TODO(terry): Should be able to always return false?
+   * Deprecated. Always returns `false`.
    */
-  bool get supportsDatabaseNames {
-    return supported &&
-        JS('bool', '!!(#.getDatabaseNames || #.webkitGetDatabaseNames)', this,
-            this);
-  }
+  @Deprecated('No longer supported on modern browsers. Always returns false.')
+  bool get supportsDatabaseNames => false;
 
   // To suppress missing implicit constructor warnings.
   factory IdbFactory._() {

tools/dom/templates/html/impl/impl_IDBFactory.darttemplate

@@ -63,13 +63,10 @@ $(ANNOTATIONS)$(NATIVESPEC)$(CLASS_MODIFIERS)class $CLASSNAME$EXTENDS$IMPLEMENTS
   }
 
   /**
-   * Checks to see if getDatabaseNames is supported by the current platform.
-   * TODO(terry): Should be able to always return false?
+   * Deprecated. Always returns `false`.
    */
-  bool get supportsDatabaseNames {
-    return supported && JS('bool',
-        '!!(#.getDatabaseNames || #.webkitGetDatabaseNames)', this, this);
-  }
+  @Deprecated('No longer supported on modern browsers. Always returns false.')
+  bool get supportsDatabaseNames => false;
 
 $!MEMBERS
 }