debug: only one evaluate on new watch expression

fixes #21524

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

@@ -927,7 +927,8 @@ export class Model implements debug.IModel {
 		const filtered = this.watchExpressions.filter(we => we.getId() === id);
 		if (filtered.length === 1) {
 			filtered[0].name = newName;
-			return filtered[0].evaluate(process, stackFrame, 'watch').then(() => {
+			// Evaluate all watch expressions again since the new watch expression might have changed some.
+			return this.evaluateWatchExpressions(process, stackFrame).then(() => {
 				this._onDidChangeWatchExpressions.fire(filtered[0]);
 			});
 		}

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

@@ -548,9 +548,7 @@ export class DebugService implements debug.IDebugService {
 	}
 
 	public renameWatchExpression(id: string, newName: string): TPromise<void> {
-		return this.model.renameWatchExpression(this.viewModel.focusedProcess, this.viewModel.focusedStackFrame, id, newName)
-			// Evaluate all watch expressions and fetch variables again since watch expression evaluation might have changed some.
-			.then(() => this.focusStackFrameAndEvaluate(this.viewModel.focusedStackFrame, this.viewModel.focusedProcess));
+		return this.model.renameWatchExpression(this.viewModel.focusedProcess, this.viewModel.focusedStackFrame, id, newName);
 	}
 
 	public moveWatchExpression(id: string, position: number): void {