src/vs/workbench/services/workingCopy/common/workingCopyHistoryTracker.ts/WorkingCopyHistoryTracker/onDidChangeContent
class WorkingCopyHistoryTracker:	private onDidChangeContent(workingCopy: IWorkingCopy): void {

		// Increment content version ID for resource
		const contentVersionId = this.getContentVersion(workingCopy.resource);
		this.workingCopyContentVersion.set(workingCopy.resource, contentVersionId + 1);
	}