Remove keyIdentifier.

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 26f8c70d90a3ae592a9ff2ec364a84ae7264e33a..c3cfa4c655a6ce2f8dea4016169003985b48c74c 100644
--- a/third_party/WebKit/Source/core/frame/Deprecation.cpp
+++ b/third_party/WebKit/Source/core/frame/Deprecation.cpp
@@ -362,9 +362,6 @@ String Deprecation::deprecationMessage(UseCounter::Feature feature)
     case UseCounter::EncryptedMediaAllSelectedContentTypesMissingCodecs:
         return String::format("EME requires that contentType strings accepted by 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(54));
 
-    case UseCounter::V8KeyboardEvent_KeyIdentifier_AttributeGetter:

[Rick Byers, 2016/07/05 14:03:59]

nit: please remove the enum entry in UseCounter.h also (the script that updates
histograms.xml is smart enough to know not to remove deleted entries).

-        return willBeRemoved("'KeyboardEvent.keyIdentifier'", 53, "5316065118650368");
-
     case UseCounter::During_Microtask_SyncXHR:
         return willBeRemoved("Invoking 'send()' on a sync XHR during microtask execution", 54, "5647113010544640");