Use Chromium BUILD to approximate Blimp protocol version, and check it.

blimp/common/BUILD.gn

 # Copyright 2015 The Chromium Authors. All rights reserved.
 # Use of this source code is governed by a BSD-style license that can be
 # found in the LICENSE file.
 
+import("//chrome/version.gni")
 import("//testing/test.gni")
 
 component("common") {
   output_name = "blimp_common"
   sources = [
     "blimp_common_export.h",
     "blob_cache/blob_cache.h",
     "blob_cache/id_util.cc",
     "blob_cache/id_util.h",
     "blob_cache/in_memory_blob_cache.cc",
     "blob_cache/in_memory_blob_cache.h",
     "compositor/blimp_task_graph_runner.cc",
     "compositor/blimp_task_graph_runner.h",
     "create_blimp_message.cc",
     "create_blimp_message.h",
     "get_client_token.cc",
     "get_client_token.h",
     "logging.cc",
     "logging.h",
-    "protocol_version.h",
     "switches.cc",
     "switches.h",
   ]
 
   defines = [ "BLIMP_COMMON_IMPLEMENTATION=1" ]
 
   deps = [
     "//base",
     "//blimp/common/proto",
     "//cc",
     "//crypto",
   ]
+
+  public_deps = [
+    ":protocol_version",
+  ]
 }
 
 source_set("test_support") {
   testonly = true
 
   sources = [
     "blob_cache/mock_blob_cache.cc",
     "blob_cache/mock_blob_cache.h",
     "blob_cache/test_util.cc",
     "blob_cache/test_util.h",
@@ skipping 21 matching lines @@
     ":common",
     ":test_support",
     "//base",
     "//blimp/common/proto",
     "//blimp/net:test_support",
     "//crypto",
     "//testing/gmock",
     "//testing/gtest",
   ]
 }
+
+process_version("protocol_version") {
+  template_file = "protocol_version.h.version"
+  output = "$target_gen_dir/protocol_version.h"
+}