Only compare unvisited background color for LayoutTheme adjustment

LayoutTests/fast/history/visited-link-button.html

Index: LayoutTests/fast/history/visited-link-button.html
diff --git a/LayoutTests/fast/history/visited-link-button.html b/LayoutTests/fast/history/visited-link-button.html
new file mode 100644
index 0000000000000000000000000000000000000000..dfacca9106c1472776a24a6c1b5f5b1cd5ba5702
--- /dev/null
+++ b/LayoutTests/fast/history/visited-link-button.html
@@ -0,0 +1,22 @@
+<script src="../../resources/js-test.js"></script>
+
+<style>
+input {
+    line-height: 10px;
+    display: none;
+}
+a:visited input {
+    background-color: yellow;
+}
+</style>
+
+<a id="a" href=""><input id="input" type="button"></input></a>
+
+<script>
+if (window.testRunner)
+    testRunner.keepWebHistory();
+
+a.style.color = "orange";
+a.style.color = "";
+shouldBeEqualToString("getComputedStyle(input).lineHeight", "normal");
+</script>