Update milestone for EME non-standard functionality

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 9b10cb52932b17d188c304ba017d9d9a154b7f93..245ff3d72fc44ddb22e6628e18ffef4b4ab8391e 100644
--- a/third_party/WebKit/Source/core/frame/Deprecation.cpp
+++ b/third_party/WebKit/Source/core/frame/Deprecation.cpp
@@ -393,7 +393,7 @@ String Deprecation::deprecationMessage(UseCounter::Feature feature) {
           "requestMediaKeySystemAccess() include codecs. Non-standard support "
           "for contentType strings without codecs will be removed in %s. "
           "Please specify the desired codec(s) as part of the contentType.",
-          milestoneString(M56));
+          milestoneString(M58));
 
     case UseCounter::VRDeprecatedFieldOfView:
       return replacedBy("VREyeParameters.fieldOfView",