+= tests fix

js/js.translator/testData/operatorOverloading/cases/overloadPlusAssignViaPlusExtensionFunction.kt

@@ -2,7 +2,7 @@ package foo
 
 import java.util.*
 
-fun <T> ArrayList<T>.plus(other: Collection<T>): List<T> {
+fun <T> ArrayList<T>.plus(other: Collection<T>): ArrayList<T> {
     val c = ArrayList<T>()
     c.addAll(this)
     c.addAll(other)

js/js.translator/testData/webDemoCanvasExamples/cases/Fancy lines.kt

@@ -43,7 +43,7 @@ class FancyLines() {
         context.bezierCurveTo(width * Math.random(), height * Math.random(),
                               width * Math.random(), height * Math.random(), x, y);
 
-        hue += Math.random() * 10;
+        hue += (Math.random() * 10).toInt();
 
         context.strokeStyle = "hsl($hue, 50%, 50%)";