src/vs/workbench/services/extensions/common/rpcProtocol.ts/MessageBuffer/sizeMixedArray
class MessageBuffer:	public static sizeMixedArray(arr: VSBuffer[], arrType: ArgType[]): number {
		let size = 0;
		size += 1; // arr length
		for (let i = 0, len = arr.length; i < len; i++) {
			const el = arr[i];
			const elType = arrType[i];
			size += 1; // arg type
			switch (elType) {
				case ArgType.String:
					size += this.sizeLongString(el);
					break;
				case ArgType.VSBuffer:
					size += this.sizeVSBuffer(el);
					break;
				case ArgType.Undefined:
					// empty...
					break;
			}
		}
		return size;
	}