Send deprecation messages for prefixed gradients now that it's possible.

third_party/WebKit/LayoutTests/fast/gradients/css3-linear-angle-gradients.html

Index: third_party/WebKit/LayoutTests/fast/gradients/css3-linear-angle-gradients.html
diff --git a/third_party/WebKit/LayoutTests/fast/gradients/css3-linear-angle-gradients.html b/third_party/WebKit/LayoutTests/fast/gradients/css3-linear-angle-gradients.html
index f5937640ed664eaa01ecaec9e4be77e697d35f6b..c00eb36a2914142a3c48475893a5aa8334fb7215 100644
--- a/third_party/WebKit/LayoutTests/fast/gradients/css3-linear-angle-gradients.html
+++ b/third_party/WebKit/LayoutTests/fast/gradients/css3-linear-angle-gradients.html
@@ -13,8 +13,7 @@
     }
 
     .linear1 {
-      background-image: -webkit-linear-gradient(white, black);
-      background-image: -moz-linear-gradient(white, black);
+      background-image: linear-gradient(white, black);
     }
     
     .linear2 {
@@ -23,18 +22,15 @@
     }
 
     .linear3 {
-      background-image: -webkit-linear-gradient(45deg, white, black);
-      background-image: -moz-linear-gradient(45deg, white, black);
+      background-image: linear-gradient(45deg, white, black);
     }
 
     .linear4 {
-      background-image: -webkit-linear-gradient(-45deg, white, black);
-      background-image: -moz-linear-gradient(-45deg, white, black);
+      background-image: linear-gradient(-225deg, white, black);

[suzyh_UTC10 (ex-contributor), 2017/04/03 01:00:05]

Since this test (and some others) now has a mix of prefixed and unprefixed
cases, and some of the unprefixed cases have involved changes to these angle
arguments, I'd feel better if someone familiar with gradients gave their OK as
well.

     }
 
     .linear5 {
-      background-image: -webkit-linear-gradient(540deg, white, black);
-      background-image: -moz-linear-gradient(540deg, white, black);
+      background-image: linear-gradient(630deg, white, black);
     }
 
     .linear6 {
@@ -53,8 +49,7 @@
     }
 
     .linear9 {
-      background-image: -webkit-linear-gradient(0deg, white -20%, blue, black 120%);
-      background-image: -moz-linear-gradient(0deg, white -20%, blue, black 120%);
+      background-image: linear-gradient(90deg, white -20%, blue, black 120%);
     }
   </style>
   <script type="text/javascript" charset="utf-8">