Add a few more edge cases to CSS serialization test.

third_party/WebKit/Source/web/tests/data/frameserializer/css/css_test_page.html

Index: third_party/WebKit/Source/web/tests/data/frameserializer/css/css_test_page.html
diff --git a/third_party/WebKit/Source/web/tests/data/frameserializer/css/css_test_page.html b/third_party/WebKit/Source/web/tests/data/frameserializer/css/css_test_page.html
index bf2b3d1048ec2f7b7b79c9986732137782ff8f4b..ac8a5d35cd395bed142c6b692295f4b992a1a81c 100644
--- a/third_party/WebKit/Source/web/tests/data/frameserializer/css/css_test_page.html
+++ b/third_party/WebKit/Source/web/tests/data/frameserializer/css/css_test_page.html
@@ -6,6 +6,17 @@
 
 <link rel="stylesheet" type="text/css" href="link_styles.css" />
 <link rel="stylesheet" type="text/css" href="encoding.css" />
+<!-- Data URL that contains an image URL. Note that it must be an absolute URL
+     as relative ones will not work from inside a data URL.
+     It's raw contents are:
+#divFuchsia {
+ background-image: url('http://www.dataurl.com/fuchsia_background.png');
+}
+-->
+<link rel="stylesheet" type="text/css" 
+      href="data:text/css;charset=utf-8,%23divFuchsia%20%7B%0D%0A%20%20background-image%3A%20url%28%27http%3A%2F%2Fwww.dataurl.com%2Ffuchsia_background.png%27%29%3B%0D%0A%7D" />
+<!-- This should be skipped for already being included from another frame -->
+<link rel="stylesheet" type="text/css" href="included_in_another_frame.css" />
 
 <style>
 @import url('import_styles.css');
@@ -60,6 +71,9 @@ ol {
   }
 }
 
+// Tries to import a CSS that was already previously linked.
+@import url('link_styles.css');
+
 </style>
 
 <script>
@@ -121,6 +135,11 @@ This div has a pink image as its background.
 This div has a brown image as its background.
 </div>
 
+<!-- Style is defined in linked data URL -->
+<div id='divFuchsia'>
+This div has a fuchsia image as its background.
+</div>
+
 Unordered list:<br>
 <ul>
   <li>Blue</li>