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

third_party/WebKit/Source/core/frame/Deprecation.cpp

Index: third_party/WebKit/Source/core/frame/Deprecation.cpp
diff --git a/third_party/WebKit/Source/core/frame/Deprecation.cpp b/third_party/WebKit/Source/core/frame/Deprecation.cpp
index 68973928d9baa66a49396dfafd04a8b383050d1a..cda002f21c29457a7444d2c7d03aa981ca3aaaaf 100644
--- a/third_party/WebKit/Source/core/frame/Deprecation.cpp
+++ b/third_party/WebKit/Source/core/frame/Deprecation.cpp
@@ -424,6 +424,24 @@ String Deprecation::DeprecationMessage(UseCounter::Feature feature) {
       return willBeRemoved("SVGPathElement.getPathSegAtLength", M62,
                            "5638783282184192");
 
+    case UseCounter::kDeprecatedWebKitLinearGradient:
+      return replacedBy("-webkit-linear-gradient", "linear-gradient");
+
+    case UseCounter::kDeprecatedWebKitRepeatingLinearGradient:
+      return replacedBy("-webkit-repeating-linear-gradient",
+                        "repeating-linear-gradient");
+
+    case UseCounter::kDeprecatedWebKitGradient:
+      return replacedBy("-webkit-gradient",
+                        "linear-gradient or radial-gradient");
+
+    case UseCounter::kDeprecatedWebKitRadialGradient:
+      return replacedBy("-webkit-radial-gradient", "radial-gradient");
+
+    case UseCounter::kDeprecatedWebKitRepeatingRadialGradient:
+      return replacedBy("-webkit-repeating-radial-gradient",
+                        "repeating-radial-gradient");
+
     // Features that aren't deprecated don't have a deprecation message.
     default:
       return String();