Remove wp_use_document_isolation_policy filter

DIP headers are sent based on browser capability alone.
The existing wp_client_side_media_processing_enabled filter
already gates the entire feature higher in the call chain.

Author: adamsilverstein

src/wp-includes/media.php

@@ -6395,13 +6395,7 @@ function wp_set_client_side_media_processing_flag(): void {
 
 	$chrome_version = wp_get_chrome_major_version();
 
-	/** This filter is documented in src/wp-includes/media.php */
-	$use_dip = apply_filters(
-		'wp_use_document_isolation_policy',
-		null !== $chrome_version && $chrome_version >= 137
-	);
-
-	if ( $use_dip ) {
+	if ( null !== $chrome_version && $chrome_version >= 137 ) {
 		wp_add_inline_script( 'wp-block-editor', 'window.__documentIsolationPolicy = true', 'before' );
 	}
 
@@ -6486,23 +6480,7 @@ function wp_set_up_cross_origin_isolation(): void {
 function wp_start_cross_origin_isolation_output_buffer(): void {
 	$chrome_version = wp_get_chrome_major_version();
 
-	/**
-	 * Filters whether to use Document-Isolation-Policy for cross-origin isolation.
-	 *
-	 * Document-Isolation-Policy provides per-document cross-origin isolation
-	 * without affecting other iframes on the page, avoiding breakage of plugins
-	 * whose iframes lose credentials/DOM access.
-	 *
-	 * @since 7.0.0
-	 *
-	 * @param bool $use_dip Whether DIP is supported and should be used.
-	 */
-	$use_dip = apply_filters(
-		'wp_use_document_isolation_policy',
-		null !== $chrome_version && $chrome_version >= 137
-	);
-
-	if ( ! $use_dip ) {
+	if ( null === $chrome_version || $chrome_version < 137 ) {
 		return;
 	}
 

tests/phpunit/tests/media/wpStartCrossOriginIsolationOutputBuffer.php

@@ -32,8 +32,6 @@ public function tear_down() {
 			ob_end_clean();
 		}
 
-		remove_all_filters( 'wp_use_document_isolation_policy' );
-
 		parent::tear_down();
 	}
 
@@ -83,34 +81,6 @@ public function test_does_not_start_output_buffer_for_safari() {
 		$this->assertSame( $level_before, $level_after, 'Output buffer should not be started for Safari.' );
 	}
 
-	/**
-	 * @runInSeparateProcess
-	 * @preserveGlobalState disabled
-	 */
-	public function test_filter_can_force_enable_dip() {
-		$_SERVER['HTTP_USER_AGENT'] = 'Mozilla/5.0 (Windows NT 10.0; rv:128.0) Gecko/20100101 Firefox/128.0';
-		add_filter( 'wp_use_document_isolation_policy', '__return_true' );
-
-		$level_before = ob_get_level();
-		wp_start_cross_origin_isolation_output_buffer();
-		$level_after = ob_get_level();
-
-		$this->assertSame( $level_before + 1, $level_after, 'Filter should force-enable output buffer.' );
-
-		ob_end_clean();
-	}
-
-	public function test_filter_can_force_disable_dip() {
-		$_SERVER['HTTP_USER_AGENT'] = 'Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/137.0.0.0 Safari/537.36';
-		add_filter( 'wp_use_document_isolation_policy', '__return_false' );
-
-		$level_before = ob_get_level();
-		wp_start_cross_origin_isolation_output_buffer();
-		$level_after = ob_get_level();
-
-		$this->assertSame( $level_before, $level_after, 'Filter should disable output buffer.' );
-	}
-
 	/**
 	 * @runInSeparateProcess
 	 * @preserveGlobalState disabled