Ensure that we don't allow 'none' alongside other values in content property

third_party/WebKit/LayoutTests/css-parser/content-parsing-invalid.html

Index: third_party/WebKit/LayoutTests/css-parser/content-parsing-invalid.html
diff --git a/third_party/WebKit/LayoutTests/css-parser/content-parsing-invalid.html b/third_party/WebKit/LayoutTests/css-parser/content-parsing-invalid.html
index 6aa63571ce7b906fef3884dacd987c389ef7c4cb..22f76bc736bc98e8174009e66b188875e0f20823 100644
--- a/third_party/WebKit/LayoutTests/css-parser/content-parsing-invalid.html
+++ b/third_party/WebKit/LayoutTests/css-parser/content-parsing-invalid.html
@@ -3,19 +3,29 @@
 <script src="../resources/testharnessreport.js"></script>
 
 <style>
-#target::before {
+#target1::before {
   content: normal normal;
 }
-#target::after {
+#target1::after {
   content: normal normal;
 }
+
+#target2::before {
+  content: none normal;

[Timothy Loh, 2016/03/30 02:53:28]

It'd make more sense to test something like none open-quote or url("a") none.
Prior to this patch, this test would pass anyway.

[nainar, 2016/03/30 03:27:36]

Done.

+}
+#target2::after {
+  content: none normal;
+}
 </style>
 
-<div id="target"></div>
+<div id="target1"></div>
+<div id="target2"></div>
 
 <script>
 test(function(){
-  assert_equals(getComputedStyle(target, '::before').content, '');
-  assert_equals(getComputedStyle(target, '::after').content, '');
+  assert_equals(getComputedStyle(target1, '::before').content, '');

[Timothy Loh, 2016/03/30 02:53:28]

btw I was too lazy to whine about this previously but it'd be better to test
this by check document.styleSheets[0].cssRules[0].style.content and similar.
getComputedStyle requires more of the pipeline than we should depend on for a
test like this. This way you won't end up needing to change it in the other
patch...

[nainar, 2016/03/30 03:27:36]

Done.

+  assert_equals(getComputedStyle(target1, '::after').content, '');
+  assert_equals(getComputedStyle(target2, '::before').content, '');
+  assert_equals(getComputedStyle(target2, '::after').content, '');
 }, "Test to ensure that invalid values of content on pseudo elements are dropped by the parser");
 </script>