カスタムキーボードでUICollectionViewを使いたいが表示されない

テスト的に書いたソースです。
表示もされません。どこが悪いのか教えていただけないでしょうか。エラーは出ませんが表示も出ません。
よろしくお願いいたします。

PS:最低限のソースに修正しました。

import UIKit

class KeyboardViewController: UIInputViewController, UICollectionViewDelegate, UICollectionViewDataSource {

    @IBOutlet var nextKeyboardButton: UIButton!

    private var lexicon: UILexicon!
    var myCollectionView : UICollectionView!

    override func updateViewConstraints() {
        super.updateViewConstraints()

        // Add custom view sizing constraints here
    }

    override func viewDidLoad() {
        super.viewDidLoad()

        // Perform custom UI setup here
        self.nextKeyboardButton = UIButton(type: .System)

        self.nextKeyboardButton.setTitle(NSLocalizedString("Next Keyboard", comment: "Title for 'Next Keyboard' button"), forState: .Normal)
        self.nextKeyboardButton.sizeToFit()
        self.nextKeyboardButton.translatesAutoresizingMaskIntoConstraints = false

        self.nextKeyboardButton.addTarget(self, action: "advanceToNextInputMode", forControlEvents: .TouchUpInside)

        self.view.addSubview(self.nextKeyboardButton)

        let nextKeyboardButtonLeftSideConstraint = NSLayoutConstraint(item: self.nextKeyboardButton, attribute: .Left, relatedBy: .Equal, toItem: self.view, attribute: .Left, multiplier: 1.0, constant: 0.0)
        let nextKeyboardButtonBottomConstraint = NSLayoutConstraint(item: self.nextKeyboardButton, attribute: .Bottom, relatedBy: .Equal, toItem: self.view, attribute: .Bottom, multiplier: 1.0, constant: 0.0)
        self.view.addConstraints([nextKeyboardButtonLeftSideConstraint, nextKeyboardButtonBottomConstraint])

        // CollectionViewのレイアウトを生成.
        let layout = UICollectionViewFlowLayout()

        // サイズの設定
        layout.itemSize.height = 20
        layout.itemSize.width = 100

        // Cell一つ一つの大きさ.
        layout.itemSize = CGSizeMake(10, 10)

        // Cellのマージン.
        layout.sectionInset = UIEdgeInsetsMake(16, 16, 32, 16)

        // セクション毎のヘッダーサイズ.
        layout.headerReferenceSize = CGSizeMake(100,30)

        // CollectionViewを生成.
        myCollectionView = UICollectionView(frame: self.view.frame, collectionViewLayout: layout)

        myCollectionView.frame.size.height = 100
        myCollectionView.frame.size.width = 100
        myCollectionView.frame.offset(dx: 100, dy: 100)

        myCollectionView.delegate = self
        print(myCollectionView.delegate)
        myCollectionView.dataSource = self
        print(myCollectionView.dataSource)



        // Cellに使われるクラスを登録.
        myCollectionView.registerClass(CustomUICollectionViewCell.self, forCellWithReuseIdentifier: "MyCell")

        myCollectionView.sizeToFit()
        print(myCollectionView.frame)


        view.addSubview(myCollectionView)


    }

    override func didReceiveMemoryWarning() {
        super.didReceiveMemoryWarning()
        // Dispose of any resources that can be recreated
    }

    override func textWillChange(textInput: UITextInput?) {
        // The app is about to change the document's contents. Perform any preparation here.
    }

    override func textDidChange(textInput: UITextInput?) {
        // The app has just changed the document's contents, the document context has been updated.

        var textColor: UIColor
        let proxy = self.textDocumentProxy
        if proxy.keyboardAppearance == UIKeyboardAppearance.Dark {
            textColor = UIColor.whiteColor()
        } else {
            textColor = UIColor.blackColor()
        }
        self.nextKeyboardButton.setTitleColor(textColor, forState: .Normal)
    }


    // MARK: - UITableViewDataSource


    /*
    Cellが選択された際に呼び出される
    */
    func collectionView(collectionView: UICollectionView, didSelectItemAtIndexPath indexPath: NSIndexPath) {

        print("Num: \(indexPath.row)")

    }

    /*
    Cellの総数を返す
    */
    func collectionView(collectionView: UICollectionView, numberOfItemsInSection section: Int) -> Int {
        return 10
    }

    /*
    Cellに値を設定する
    */
    func collectionView(collectionView: UICollectionView, cellForItemAtIndexPath indexPath: NSIndexPath) -> UICollectionViewCell {

        let cell : CustomUICollectionViewCell = collectionView.dequeueReusableCellWithReuseIdentifier("MyCell", forIndexPath: indexPath) as! CustomUICollectionViewCell
        cell.textLabel?.text = indexPath.row.description

        return cell
    }
}

class CustomUICollectionViewCell : UICollectionViewCell{

    var textLabel : UILabel?

    required init?(coder aDecoder: NSCoder) {
        super.init(coder: aDecoder)
    }

    override init(frame: CGRect) {
        super.init(frame: frame)

        // UILabelを生成.
        textLabel = UILabel(frame: CGRectMake(0, 0, frame.width, frame.height))
        textLabel?.text = "nil"
        textLabel?.backgroundColor = UIColor.whiteColor()
        textLabel?.textAlignment = NSTextAlignment.Center

        // Cellに追加.
        self.contentView.addSubview(textLabel!)
    }

}