Allow output channel to stay in scroll position

fixes #3351

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

@@ -154,11 +154,14 @@ export class StringEditor extends BaseTextEditor {
 
 	/**
 	 * Reveals the last line of this editor if it has a model set.
+	 * If smart reveal is true will only reveal the last line if the line before last is visible #3351
 	 */
-	public revealLastLine(): void {
+	public revealLastLine(smartReveal = false): void {
 		let codeEditor = <ICodeEditor>this.getControl();
 		let model = codeEditor.getModel();
-		if (model) {
+		const lineBeforeLastRevealed = codeEditor.getScrollTop() + codeEditor.getLayoutInfo().height >= codeEditor.getScrollHeight();
+
+		if (model && (!smartReveal || lineBeforeLastRevealed)) {
 			let lastLine = model.getLineCount();
 			codeEditor.revealLine(lastLine);
 		}

src/vs/workbench/parts/output/browser/outputEditorInput.ts

@@ -77,7 +77,7 @@ export class OutputEditorInput extends StringEditorInput {
 		this.bufferedOutput = '';
 
 		const panel = this.panelService.getActivePanel();
-		(<OutputPanel>panel).revealLastLine();
+		(<OutputPanel>panel).revealLastLine(true);
 	}
 
 	private onOutputReceived(e: IOutputEvent): void {