Deprecate FileReaderSync in service workers.

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 b9d0ff385642d88f55a65c64e752bc44d5864c93..0674c2ae7da096d8c5a3283f9bdca6a74e612a70 100644
--- a/third_party/WebKit/Source/core/frame/Deprecation.cpp
+++ b/third_party/WebKit/Source/core/frame/Deprecation.cpp
@@ -407,6 +407,10 @@ String Deprecation::deprecationMessage(UseCounter::Feature feature) {
           "-internal-media-controls-text-track-list* selectors", M59,
           "5661431349379072");
 
+    case UseCounter::FileReaderSyncInServiceWorker:
+      return willBeRemoved("FileReaderSync in service workers", M59,
+                           "5739144722513920");
+
     // Features that aren't deprecated don't have a deprecation message.
     default:
       return String();