[Nearby Connections] Add OS_INFO at initial connection for BWU protocol.

PiperOrigin-RevId: 508561261
diff --git a/connections/implementation/proto/offline_wire_formats.proto b/connections/implementation/proto/offline_wire_formats.proto
index 2d4758c..b93c47b 100644
--- a/connections/implementation/proto/offline_wire_formats.proto
+++ b/connections/implementation/proto/offline_wire_formats.proto
@@ -118,6 +118,7 @@
     REJECT = 2;
   }
   optional ResponseStatus response = 3;
+  optional OsInfo os_info = 4;
 }
 
 message PayloadTransferFrame {
@@ -373,3 +374,17 @@
     ISO_3166_1_ALPHA_2 = 2;
   }
 }
+
+// Device capability for OS information.
+message OsInfo {
+  enum OsType {
+    UNKNOWN_OS_TYPE = 0;
+    ANDROID = 1;
+    CHROME_OS = 2;
+    WINDOWS = 3;
+    APPLE = 4;
+    LINUX = 100;  // g3 test environment
+  }
+
+  optional OsType type = 1;
+}
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