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 2f62ff31a638e61653b0199050639fa904c56787..2b05e113f171f8c734c4d120511cf314c5273c0d 100644
--- a/third_party/WebKit/Source/core/frame/Deprecation.cpp
+++ b/third_party/WebKit/Source/core/frame/Deprecation.cpp
@@ -426,6 +426,24 @@ String Deprecation::deprecationMessage(UseCounter::Feature feature) {
                                    "the 'script-src' directive for Workers",
                                    M60, "5922594955984896");
 
+    case UseCounter::DeprecatedWebKitLinearGradient:
+      return replacedBy("-webkit-linear-gradient", "linear-gradient");
+
+    case UseCounter::DeprecatedWebKitRepeatingLinearGradient:
+      return replacedBy("-webkit-repeating-linear-gradient",
+                        "repeating-linear-gradient");
+
+    case UseCounter::DeprecatedWebKitGradient:
+      return replacedBy("-webkit-gradient",
+                        "linear-gradient or radial-gradient");
+
+    case UseCounter::DeprecatedWebKitRadialGradient:
+      return replacedBy("-webkit-radial-gradient", "radial-gradient");
+
+    case UseCounter::DeprecatedWebKitRepeatingRadialGradient:
+      return replacedBy("-webkit-repeating-radial-gradient",
+                        "repeating-radial-gradient");
+
     // Features that aren't deprecated don't have a deprecation message.
     default:
       return String();