Allow the cast tray to function as expected when the installed extension is missing API methods.

BUG=489445

Review URL: https://codereview.chromium.org/1145833003

Cr-Commit-Position: refs/heads/master@{#330663}
CastTrayView::~CastTrayView() {
}

CastTrayView::~CastTrayView() {
}
