debug: tune watch expressions pane delaying

fixes #14499

src/vs/workbench/parts/debug/common/debugModel.ts

@@ -207,8 +207,12 @@ export class Expression extends ExpressionContainer implements debug.IExpression
 
 	constructor(public name: string, cacheChildren: boolean, id = generateUuid()) {
 		super(null, 0, id, cacheChildren, 0, 0);
-		this.value = Expression.DEFAULT_VALUE;
 		this.available = false;
+		// name is not set if the expression is just being added
+		// in that case do not set default value to prevent flashing #14499
+		if (name) {
+			this.value = Expression.DEFAULT_VALUE;
+		}
 	}
 
 	public evaluate(process: debug.IProcess, stackFrame: debug.IStackFrame, context: string): TPromise<void> {

src/vs/workbench/parts/debug/electron-browser/debugService.ts

@@ -641,7 +641,8 @@ export class DebugService implements debug.IDebugService {
 			const process = this.model.addProcess(configuration.name, session);
 
 			if (!this.viewModel.focusedProcess) {
-				this.setFocusedStackFrameAndEvaluate(null, process);
+				this.viewModel.setFocusedStackFrame(null, process);
+				this._onDidChangeState.fire();
 			}
 			this.toDisposeOnSessionEnd[session.getId()] = [];
 			if (client) {

src/vs/workbench/parts/debug/electron-browser/debugViewer.ts

@@ -56,7 +56,7 @@ export function renderExpressionValue(expressionOrValue: debug.IExpression | str
 		dom.addClass(container, 'string');
 	}
 
-	if (showChanged && (<any>expressionOrValue).valueChanged) {
+	if (showChanged && (<any>expressionOrValue).valueChanged && value !== Expression.DEFAULT_VALUE) {
 		// value changed color has priority over other colors.
 		container.className = 'value changed';
 	}

src/vs/workbench/parts/debug/electron-browser/debugViews.ts

@@ -177,7 +177,7 @@ export class WatchExpressionsView extends CollapsibleViewletView {
 			this.tree.refresh().done(() => {
 				return this.toReveal instanceof Expression ? this.tree.reveal(this.toReveal) : TPromise.as(true);
 			}, errors.onUnexpectedError);
-		}, 250);
+		}, 50);
 	}
 
 	public renderHeader(container: HTMLElement): void {