Update the deprecation message of /deep/ and remove that of ::shadow

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 6ad05bf03c5caa89fc34fffe5790fa6aebd040f5..270163347edb1ebdcff5f8027b86f5eb56708d52 100644
--- a/third_party/WebKit/Source/core/frame/Deprecation.cpp
+++ b/third_party/WebKit/Source/core/frame/Deprecation.cpp
@@ -349,14 +349,11 @@ String Deprecation::DeprecationMessage(UseCounter::Feature feature) {
              "details.";
 
     case UseCounter::kCSSDeepCombinator:
-      return String::Format(
-          "/deep/ combinator is deprecated and will be a no-op in %s. See "
-          "https://www.chromestatus.com/features/4964279606312960 for more "
-          "details.",
-          milestoneString(M60));
-
-    case UseCounter::kCSSSelectorPseudoShadow:
-      return willBeRemoved("::shadow pseudo-element", M60, "6750456638341120");
+      return "/deep/ combinator is no longer supported in CSS dynamic profile. "
+             "It is now effectively no-op, acting as if it were a descendant "
+             "combinator. You should consider to remove it. See "
+             "https://www.chromestatus.com/features/4964279606312960 for more "
+             "details.";
 
     case UseCounter::kVREyeParametersOffset:
       return replacedBy("VREyeParameters.offset",