diff --git a/third_party/WebKit/LayoutTests/http/tests/security/powerfulFeatureRestrictions/old-powerful-features-on-insecure-origin-expected.txt b/third_party/WebKit/LayoutTests/http/tests/security/powerfulFeatureRestrictions/old-powerful-features-on-insecure-origin-expected.txt
index 50effe2..e04c515fc 100644
--- a/third_party/WebKit/LayoutTests/http/tests/security/powerfulFeatureRestrictions/old-powerful-features-on-insecure-origin-expected.txt
+++ b/third_party/WebKit/LayoutTests/http/tests/security/powerfulFeatureRestrictions/old-powerful-features-on-insecure-origin-expected.txt
@@ -3,7 +3,7 @@
 CONSOLE WARNING: line 32: The deviceorientation event is deprecated on insecure origins, and support will be removed in the future. You should consider switching your application to a secure origin, such as HTTPS. See https://goo.gl/rStTGz for more details.
 CONSOLE WARNING: line 42: getCurrentPosition() and watchPosition() no longer work on insecure origins. To use this feature, you should consider switching your application to a secure origin, such as HTTPS. See https://goo.gl/rStTGz for more details.
 CONSOLE WARNING: line 61: getUserMedia() no longer works on insecure origins. To use this feature, you should consider switching your application to a secure origin, such as HTTPS. See https://goo.gl/rStTGz for more details.
-CONSOLE WARNING: line 36: requestMediaKeySystemAccess() is deprecated on insecure origins in the specification. Support will be removed in the future. You should consider switching your application to a secure origin, such as HTTPS. See https://goo.gl/rStTGz for more details.
+CONSOLE WARNING: line 36: Using requestMediaKeySystemAccess() on insecure origins is deprecated and will be removed in M58, around April 2017. You should consider switching your application to a secure origin, such as HTTPS. See https://goo.gl/rStTGz for more details.
 This is a testharness.js-based test.
 PASS device motion 
 PASS device orientation 
diff --git a/third_party/WebKit/Source/core/frame/Deprecation.cpp b/third_party/WebKit/Source/core/frame/Deprecation.cpp
index 2757290..3b7c019 100644
--- a/third_party/WebKit/Source/core/frame/Deprecation.cpp
+++ b/third_party/WebKit/Source/core/frame/Deprecation.cpp
@@ -315,10 +315,12 @@
              "details.";
 
     case UseCounter::EncryptedMediaInsecureOrigin:
-      return "requestMediaKeySystemAccess() is deprecated on insecure origins "
-             "in the specification. Support will be removed in the future. You "
-             "should consider switching your application to a secure origin, "
-             "such as HTTPS. See https://goo.gl/rStTGz for more details.";
+      return String::format(
+          "Using requestMediaKeySystemAccess() on insecure origins is "
+          "deprecated and will be removed in %s. You should consider "
+          "switching your application to a secure origin, such as HTTPS. See "
+          "https://goo.gl/rStTGz for more details.",
+          milestoneString(M58));
 
     case UseCounter::MediaSourceAbortRemove:
       return "Using SourceBuffer.abort() to abort remove()'s asynchronous "