Edit in JSFiddle

Width: 200px
<d-linear-layout vertical="false" style="width: 200px; border: solid 1px black">    
    <div class="blue" style="width:150px">150px</div>
    <div class="green fill">B</div>
    <div class="red">C</div>
</d-linear-layout> 
Width: 100%
<d-linear-layout vertical="false" style="width: 100%; border: solid 1px black">    
    <div class="blue" style="width:30%">30%</div>
    <div class="green fill">B</div>
    <div class="red">C</div>
</d-linear-layout> 

.red { background-color: #D9534F; }
.blue { background-color: #5BC0DE; }
.green { background-color: #5CB85C;}

require.config({
    baseUrl: "http://ibm-js.github.io/libraries/master"
});
require(["deliteful-build/layer"], function () {
    require([
        "deliteful/LinearLayout"
    ], function (){
        document.body.style.display = "";
    });
});