[WebCrypto] Use Deprecation instead of UseCounter

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 86fb5c497dfb42031fc250d11f9a925027eb4728..680e4f5ccbe8bc1406af3ada750e2b5988287438 100644
--- a/third_party/WebKit/Source/core/frame/Deprecation.cpp
+++ b/third_party/WebKit/Source/core/frame/Deprecation.cpp
@@ -423,6 +423,9 @@ String Deprecation::deprecationMessage(UseCounter::Feature feature) {
              "https://www.chromestatus.com/features/6680566019653632 for more "
              "details.";
 
+    case UseCounter::SubtleCryptoOnlyStrictSecureContextCheckFailed:
+      return "WebCrypto requires secure origin to be used.";

[Mike West, 2017/02/23 15:39:53]

How about something like:

```
return String::format(
  "Web Crypto API usage inside secure frames with non-secure ancestors is
deprecated."
  "The API will no longer be exposed in these contexts as of %s. See "
  "[link to chromestatus entry] for more details.",
  milestoneString(M59));
```

+
     // Features that aren't deprecated don't have a deprecation message.
     default:
       return String();