CSS Animation Oscillating Flip X axis - css

Question

I have a CSS3 Animation for an indeterminate progress bar. In the animation I have a gradient oscillating back and forth along the progress bar. I would like to flip the image of gradient horizonally as it travels back to the left side of the progress bar. Basically the gradient always fades out the opposite direction the image is moving. Unfortunately I can't figure out a way for the image to flip horizontally BEFORE it starts moving back towards the left and am getting some odd transformations of the image as it flips.
I have created a JSFiddle to show how it looks right now.
http://jsfiddle.net/MtWzL/
Here is the CSS I'm currently using for the animation:
#-webkit-keyframes loader {
0% {
-webkit-transform: scaleX(1);
-webkit-transform: translateX(-100px);
-webkit-transform-origin:left;
}
50% {
-webkit-transform: translateX(300px);
}
100% {
-webkit-transform: translateX(-100px);
-webkit-transform: scaleX(-1);
}
}
#keyframes loader {
0% {
transform: scaleX(1);
transform: translateX(-100px);
transform-origin:left;
}
50% {
transform: translateX(300px);
}
100% {
transform: translateX(-100px);
transform: scaleX(-1);
}
}
.slider
{
animation: loader 2.5s infinite linear;
-webkit-animation: loader 2.5s infinite linear; /* Safari and Chrome */
background: url('http://s23.postimg.org/mglkwgxuv/indeterminate_bg.png') no-repeat;
border-radius: 10px;
height: 10px;
position: relative;
width: 100px;
z-index: 999;
opacity: .6;
}
.container {
background: -webkit-linear-gradient(#00c3ff,#0071bc);
background: linear-gradient(#00c3ff,#0071bc);
border-radius: 3px;
height: 10px;
overflow: hidden;
width: 300px;
}
.background {
background: rgba(0,0,0,0.7);
border-radius: 3px;
display: inline-block;
padding: 10px;
}

Answer 1

There are 2 issues that need to be fixed
first of all, this
-webkit-transform: scaleX(1);
-webkit-transform: translateX(-100px);
won't work as you expect; the second property over-rides the first one, as you can not set 2 different values for a property in separate lines.
the correct syntax would be
-webkit-transform: translateX(-100px) scaleX(1);
And second, if you want a sudden change in some value, you need to set it from a keyframe to another keyframe close enough to the first one.
So, the solution would be
#-webkit-keyframes loader {
0% { -webkit-transform: translateX(-100px) scaleX(1); }
50% { -webkit-transform: translateX(300px) scaleX(1); }
51% { -webkit-transform: translateX(300px) scaleX(-1); }
100% { -webkit-transform: translateX(-100px) scaleX(-1); }
}
corrected fiddle
I have corrected only the webkit transforms, but the same concept applies to the rest.

Answer 2

I was watching for your problem since you put it here, but I guess its some kind of bug we won't solve or maybe I just dont understand why it is working like that.
Since I had no clue how to solve it I manage to do example for you with alternative solution
EXAMPLE
As you can see I modified your jsfiddle, simple words, created another slide loader .sliderBack that goes backwards. Hope it will helps you somehow. Peace :)