output: limit buffer

fixes #4127

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

@@ -83,7 +83,11 @@ export class OutputEditorInput extends StringEditorInput {
 	private onOutputReceived(e: IOutputEvent): void {
 		if (this.outputSet && e.channel === this.channel) {
 			if (e.output) {
-				this.bufferedOutput += e.output;
+				if (this.bufferedOutput.length + e.output.length > MAX_OUTPUT_LENGTH) {
+					this.bufferedOutput = '...' + this.bufferedOutput.substr(this.bufferedOutput.length + e.output.length - MAX_OUTPUT_LENGTH);
+				}
+
+				this.bufferedOutput += e.output.substr(0, MAX_OUTPUT_LENGTH);
 				this.scheduleOutputAppend();
 			} else if (e.output === null) {
 				this.clearValue(); // special output indicates we should clear