theme - restore tabs flicker protection

src/vs/workbench/browser/parts/editor/media/tabstitle.css

@@ -5,7 +5,11 @@
 
 /* Title Container */
 
-.hc-black .monaco-workbench > .part.editor > .content > .one-editor-silo > .container > .title.tabs.shows-tabs {
+.monaco-workbench > .part.editor > .content > .one-editor-silo > .container > .title.empty {
+	background: inherit !important; /* prevents some ugly flickering when opening first tab */
+}
+
+.hc-black .monaco-workbench > .part.editor > .content > .one-editor-silo > .container > .title.tabs {
 	border-bottom: 1px solid;
 }
 
@@ -182,7 +186,7 @@
 
 /* TODO@theme */
 
-.hc-black .monaco-workbench > .part.editor > .content > .one-editor-silo > .container > .title.tabs.shows-tabs {
+.hc-black .monaco-workbench > .part.editor > .content > .one-editor-silo > .container > .title.tabs {
 	border-bottom-color: #6FC3DF;
 }
 

src/vs/workbench/browser/parts/editor/tabsTitleControl.ts

@@ -351,7 +351,7 @@ export class TabsTitleControl extends TitleControl {
 
 		// Handle Tabs
 		this.handleTabs(group.count);
-		DOM.addClass(this.titleContainer, 'shows-tabs');
+		DOM.removeClass(this.titleContainer, 'empty');
 
 		// Update Tabs
 		this.doUpdate();
@@ -363,7 +363,7 @@ export class TabsTitleControl extends TitleControl {
 		this.tabDisposeables = dispose(this.tabDisposeables);
 		this.editorLabels = [];
 
-		DOM.removeClass(this.titleContainer, 'shows-tabs');
+		DOM.addClass(this.titleContainer, 'empty');
 	}
 
 	private handleTabs(tabsNeeded: number): void {