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 bff97717e7d01258c7c264ad14774328a8e33e77..e24986b6541c09b22889eaf10cd6546a016d2301 100644
--- a/third_party/WebKit/Source/core/frame/Deprecation.cpp
+++ b/third_party/WebKit/Source/core/frame/Deprecation.cpp
@@ -430,6 +430,10 @@ 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();