[cast_runner] Modify syntax of CrKey UserAgent version.

Adds an additional minor version suffix to the hardcoded CrKey version
string.

Bug: 1071138, b/143307063
Change-Id: Iacbc48bd90e8d9bbdf725e57209a654ef68afc4c
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2150061
Auto-Submit: Kevin Marshall <kmarshall@chromium.org>
Commit-Queue: David Dorwin <ddorwin@chromium.org>
Reviewed-by: David Dorwin <ddorwin@chromium.org>
Cr-Commit-Position: refs/heads/master@{#760181}

fuchsia/runners/cast/main.cc

@@ -58,7 +58,7 @@ fuchsia::web::CreateContextParams CreateMainContextParams() {
 
   // TODO(b/141956135): Use CrKey version provided by the Agent.
   create_context_params.set_user_agent_product("CrKey");
-  create_context_params.set_user_agent_version("1.43");
+  create_context_params.set_user_agent_version("1.43.000000");
 
   create_context_params.set_remote_debugging_port(
       CastRunner::kRemoteDebuggingPort);