Add deprecation messages for blocked subresource types.

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 07966da0a2cc21a091c2b2102b5f5f9efe966eba..e19e36890d9944098d25f423c8aea77947267231 100644
--- a/third_party/WebKit/Source/core/frame/Deprecation.cpp
+++ b/third_party/WebKit/Source/core/frame/Deprecation.cpp
@@ -263,6 +263,24 @@ String Deprecation::deprecationMessage(UseCounter::Feature feature) {
     case UseCounter::RangeExpand:
       return replacedBy("'Range.expand()'", "'Selection.modify()'");
 
+    // Blocked subresource requests:
+    case UseCounter::LegacyProtocolEmbeddedAsSubresource:
+      return String::format(
+          "Subresource requests using legacy protocols (like `ftp:`) are "
+          "deprecated, and will be blocked in %s. Please deliver "
+          "web-accessible resources over modern protocols like HTTPS. "
+          "See https://www.chromestatus.com/feature/5709390967472128 for more "
+          "details.",
+          milestoneString(M59));
+
+    case UseCounter::RequestedSubresourceWithEmbeddedCredentials:
+      return String::format(
+          "Subresource requests whose URLs contain embedded credentials (e.g. "
+          "`https://user:pass@host/`) are deprecated, and will be blocked in "
+          "%s. See https://www.chromestatus.com/feature/5669008342777856 for "
+          "more details.",
+          milestoneString(M59));
+
     // Powerful features on insecure origins (https://goo.gl/rStTGz)
     case UseCounter::DeviceMotionInsecureOrigin:
       return "The devicemotion event is deprecated on insecure origins, and "