Revert "Fix theme not being synchronized with external windows on firefox" (#260252)

Revert "Fix theme not being synchronized with external windows on firefox (#2…"

This reverts commit 5a03ce4.

Author: bpasero

src/vs/base/browser/domStylesheets.ts

@@ -5,7 +5,6 @@
 
 import { DisposableStore, toDisposable, IDisposable } from '../common/lifecycle.js';
 import { autorun, IObservable } from '../common/observable.js';
-import { isFirefox } from './browser.js';
 import { getWindows, sharedMutationObserver } from './dom.js';
 import { mainWindow } from './window.js';
 
@@ -98,15 +97,7 @@ function cloneGlobalStyleSheet(globalStylesheet: HTMLStyleElement, globalStylesh
 		clone.sheet?.insertRule(rule.cssText, clone.sheet?.cssRules.length);
 	}
 
-	let observeInit: MutationObserverInit = { childList: true };
-	if (isFirefox) {
-		// Firefox doesn't support observing style tag contents
-		// As a workaround, also observe the data-version attribute
-		// that is updated when the content is updated
-		observeInit = { ...observeInit, attributes: true, attributeFilter: ['data-version'] };
-	}
-
-	disposables.add(sharedMutationObserver.observe(globalStylesheet, disposables, observeInit)(() => {
+	disposables.add(sharedMutationObserver.observe(globalStylesheet, disposables, { childList: true })(() => {
 		clone.textContent = globalStylesheet.textContent;
 	}));
 

src/vs/workbench/services/themes/browser/workbenchThemeService.ts

@@ -33,7 +33,7 @@ import { updateColorThemeConfigurationSchemas, updateFileIconThemeConfigurationS
 import { ProductIconThemeData, DEFAULT_PRODUCT_ICON_THEME_ID } from './productIconThemeData.js';
 import { registerProductIconThemeSchemas } from '../common/productIconThemeSchema.js';
 import { ILogService } from '../../../../platform/log/common/log.js';
-import { isFirefox, isWeb } from '../../../../base/common/platform.js';
+import { isWeb } from '../../../../base/common/platform.js';
 import { ColorScheme, ThemeTypeSelector } from '../../../../platform/theme/common/theme.js';
 import { IHostColorSchemeService } from '../common/hostColorSchemeService.js';
 import { RunOnceScheduler, Sequencer } from '../../../../base/common/async.js';
@@ -42,7 +42,6 @@ import { getIconsStyleSheet } from '../../../../platform/theme/browser/iconsStyl
 import { asCssVariableName, getColorRegistry } from '../../../../platform/theme/common/colorRegistry.js';
 import { ILanguageService } from '../../../../editor/common/languages/language.js';
 import { mainWindow } from '../../../../base/browser/window.js';
-import { generateUuid } from '../../../../base/common/uuid.js';
 
 // implementation
 
@@ -794,21 +793,13 @@ class ThemeFileWatcher {
 }
 
 function _applyRules(styleSheetContent: string, rulesClassName: string) {
-	let themeStyle = mainWindow.document.head.getElementsByClassName(rulesClassName).item(0);
-	if (!themeStyle) {
-		themeStyle = createStyleSheet();
-		themeStyle.className = rulesClassName;
-	}
-
-	if (themeStyle.textContent !== styleSheetContent) {
-		themeStyle.textContent = styleSheetContent;
-
-		if (isFirefox) {
-			// Firefox doesn't support observing style tag contents
-			// As a workaround, also update the data-version attribute
-			// when it changes so it can be observed
-			themeStyle.setAttribute('data-version', generateUuid());
-		}
+	const themeStyles = mainWindow.document.head.getElementsByClassName(rulesClassName);
+	if (themeStyles.length === 0) {
+		const elStyle = createStyleSheet();
+		elStyle.className = rulesClassName;
+		elStyle.textContent = styleSheetContent;
+	} else {
+		(<HTMLStyleElement>themeStyles[0]).textContent = styleSheetContent;
 	}
 }