Announce to Omaha that Chrome accepts CRX₂ and CRX₃ files.

components/update_client/protocol_builder.cc

Index: components/update_client/protocol_builder.cc
diff --git a/components/update_client/protocol_builder.cc b/components/update_client/protocol_builder.cc
index 12fdfbc971860df1f9afe2e3ebb5bcbbcd4bd234..ab273ffe0edc13a2c84d732f7a2636ebe46aa797 100644
--- a/components/update_client/protocol_builder.cc
+++ b/components/update_client/protocol_builder.cc
@@ -182,6 +182,9 @@ std::string BuildProtocolRequest(
   if (!additional_attributes.empty())
     base::StringAppendF(&request, "%s ", additional_attributes.c_str());
 
+  // Constant information for this updater.
+  base::StringAppendF(&request, "dedup=\"cr\" acceptformat=\"crx2,crx3\" ");
+
   // Chrome version and platform information.
   base::StringAppendF(
       &request,