Implement ::placeholder CSS selector.

third_party/WebKit/LayoutTests/fast/forms/text/placeholder-pseudo-style.html

Index: third_party/WebKit/LayoutTests/fast/forms/text/placeholder-pseudo-style.html
diff --git a/third_party/WebKit/LayoutTests/fast/forms/text/placeholder-pseudo-style.html b/third_party/WebKit/LayoutTests/fast/forms/text/placeholder-pseudo-style.html
index 23cb50901bc22cfd963e0ebce97bc78c8dc09c01..7328ee76fbaec67df9bb73dc46b4863f148f3826 100644
--- a/third_party/WebKit/LayoutTests/fast/forms/text/placeholder-pseudo-style.html
+++ b/third_party/WebKit/LayoutTests/fast/forms/text/placeholder-pseudo-style.html
@@ -2,11 +2,51 @@
 input.red::-webkit-input-placeholder {
     color: rgb(100, 0, 0);
 }
+
+.blue::placeholder {
+    color: blue;
+}
+
+.prefixed-unprefixed::-webkit-input-placeholder {
+    color: red;
+}
+.prefixed-unprefixed::placeholder {
+    color: blue;
+}
+
+.unprefixed-prefixed::placeholder {
+    color: blue;
+}
+.unprefixed-prefixed::-webkit-input-placeholder {
+    color: red;
+}
 </style>
-This tests that you can set the placeholder text color.<br>
+This tests that you can set the placeholder text color.
+
+<div>
+Default style:
+<input placeholder="default">
+<input placeholder="default disabled">
+</div>
+
+<div>
+::-webkit-input-placeholder:
 <input class="red" placeholder="text">
 <input class="red" type="search" placeholder="search">
 <input class="red" type="password" placeholder="password">
 <input class="red" disabled placeholder="disabled text">
-<input placeholder="default">
-<input placeholder="default disabled">
+</div>
+
+<div>
+::placeholder:
+<input class="blue" placeholder="text">
+<input class="blue" type="search" placeholder="search">
+<input class="blue" type="password" placeholder="password">
+<input class="blue" disabled placeholder="disabled text">
+</div>
+
+<div>
+Both:
+<input class="prefixed-unprefixed" placeholder="unprefixed">
+<input class="unprefixed-prefixed" placeholder="prefixed">
+</div>