Add CSS class when icons are shown (fixes #19501)

src/vs/workbench/parts/walkThrough/electron-browser/walkThroughPart.css

@@ -139,7 +139,7 @@
 	white-space: pre;
 }
 
-.show-file-icons .vs_code_editor_walkthrough\.md-name-file-icon.md-ext-file-icon.markdown-lang-file-icon.file-icon::before {
+.file-icons-enabled .show-file-icons .vs_code_editor_walkthrough\.md-name-file-icon.md-ext-file-icon.markdown-lang-file-icon.file-icon::before {
 	content: ' ';
 	background-image: url('../../../../../../resources/code-icon.svg');
 }

src/vs/workbench/parts/welcomePage/electron-browser/welcomePage.css

@@ -258,7 +258,7 @@
 	display: none;
 }
 
-.show-file-icons .vs_code_welcome_page\.html-name-file-icon.html-ext-file-icon.html-lang-file-icon.file-icon::before {
+.file-icons-enabled .show-file-icons .vs_code_welcome_page\.html-name-file-icon.html-ext-file-icon.html-lang-file-icon.file-icon::before {
 	content: ' ';
 	background-image: url('../../../../../../resources/code-icon.svg');
 }

src/vs/workbench/services/themes/electron-browser/themeService.ts

@@ -41,6 +41,8 @@ let defaultBaseTheme = getBaseThemeId(DEFAULT_THEME_ID);
 const defaultThemeExtensionId = 'vscode-theme-defaults';
 const oldDefaultThemeExtensionId = 'vscode-theme-colorful-defaults';
 
+const fileIconsEnabledClass = 'file-icons-enabled';
+
 function validateThemeId(theme: string): string {
 	// migrations
 	switch (theme) {
@@ -496,6 +498,13 @@ export class ThemeService implements IThemeService {
 			} else {
 				this.currentIconTheme = noFileIconTheme;
 			}
+			if (this.container) {
+				if (newIconTheme) {
+					$(this.container).addClass(fileIconsEnabledClass);
+				} else {
+					$(this.container).removeClass(fileIconsEnabledClass);
+				}
+			}
 
 			this.storageService.store(ICON_THEME_PREF, this.currentIconTheme.id, StorageScope.GLOBAL);
 			if (broadcastToAllWindows) {