src/vs/editor/browser/widget/diffEditorWidget.ts/ViewZonesComputer/_getViewLineCount
class ViewZonesComputer:	private static _getViewLineCount(editor: CodeEditorWidget, startLineNumber: number, endLineNumber: number): number {
		const model = editor.getModel();
		const viewModel = editor._getViewModel();
		if (model && viewModel) {
			const viewRange = getViewRange(model, viewModel, startLineNumber, endLineNumber);
			return (viewRange.endLineNumber - viewRange.startLineNumber + 1);
		}

		return (endLineNumber - startLineNumber + 1);
	}