TL;DR

With a comma, you can specify multiple animations each with their own properties as stated in the CriticalError answer below.

Example:

animation: rotate 1s, spin 3s;

Original answer

There are two issues here:

#1

-webkit-animation:spin 2s linear infinite;
-webkit-animation:scale 4s linear infinite;

The second line replaces the first one. So, has no effect.

#2

Both keyframes applies on the same property transform

As an alternative you could to wrap the image in a <div> and animate each one separately and at different speeds.

http://jsfiddle.net/rnrlabs/x9cu53hp/

.scaler {
    position: absolute;
    top: 100%;
    left: 50%;
    width: 120px;
    height: 120px;
    margin:-60px 0 0 -60px;
    animation: scale 4s infinite linear;    
}

.spinner {
    position: relative;
    top: 150px;
    animation: spin 2s infinite linear;
}


@keyframes spin { 
    100% { 
        transform: rotate(180deg);
    } 
}

@keyframes scale {
    100% {
         transform: scaleX(2) scaleY(2);
    }
}

<div class="spinner">
<img class="scaler" src="http://makeameme.org/media/templates/120/grumpy_cat.jpg" alt="" width="120" height="120">
<div>