cssanimation: Compute progress correctly

We were computing the wrong progress, in particular when the iteration
count was non-integer.

Test included.

testsuite/reftests/Makefile.am

@@ -83,6 +83,9 @@ testdata = \
 	animation-direction.css \
 	animation-direction.ref.ui \
 	animation-direction.ui \
+	animation-fill-mode-iteration-count.css \
+	animation-fill-mode-iteration-count.ref.ui \
+	animation-fill-mode-iteration-count.ui \
 	background-area.css \
 	background-area.ref.ui \
 	background-area.ui \

testsuite/reftests/animation-fill-mode-iteration-count.css

@@ -0,0 +1,83 @@
+@keyframes cssrocks {
+  from { background-color: yellow; }
+  to   { background-color: red; }
+}
+
+box {
+  background-color: blue;
+  animation-fill-mode: both;
+  animation-duration: 100s;
+  padding: 1px;
+  background-clip: content-box;
+  animation-timing-function: linear;
+}
+
+.after {
+  animation-name: cssrocks;
+  animation-delay: -10000s;
+}
+
+.before {
+  animation-name: cssrocks;
+  animation-delay: 10000s;
+}
+
+.normal {
+  animation-direction: normal;
+}
+
+.reverse {
+  animation-direction: reverse;
+}
+
+.alternate {
+  animation-direction: alternate;
+}
+
+.alternate-reverse {
+  animation-direction: alternate-reverse;
+}
+
+.x0 {
+  animation-iteration-count: 0;
+}
+
+.x02 {
+  animation-iteration-count: 0.2;
+}
+
+.x1 {
+  animation-iteration-count: 1;
+}
+
+.x12 {
+  animation-iteration-count: 1.2;
+}
+
+.x2 {
+  animation-iteration-count: 2;
+}
+
+.x22 {
+  animation-iteration-count: 2.2;
+}
+
+.yellow {
+  animation: none;
+  background-color: yellow;
+}
+
+.red {
+  animation: none;
+  background-color: red;
+}
+
+.darkorange {
+  animation: none;
+  background-color: rgb(255,51,0);
+}
+
+.lightorange {
+  animation: none;
+  background-color: rgb(255,204,0);
+}