Remove all //blimp code.

components/metrics/BUILD.gn

 # Copyright 2014 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.
 
-declare_args() {
-  # Overrides os name in uma metrics log to "Blimp".
-  metrics_use_blimp = false
-}
-
-# These are only used by the blimp team, which has entirely migrated to gn,
-# so this logic is not replicated in the gyp file.
-if (metrics_use_blimp) {
-  defines = [ "OVERRIDE_OS_NAME_TO_BLIMP" ]
-}
-
 static_library("metrics") {
   sources = [
     "call_stack_profile_metrics_provider.cc",
     "call_stack_profile_metrics_provider.h",
     "clean_exit_beacon.cc",
     "clean_exit_beacon.h",
     "client_info.cc",
     "client_info.h",
     "cloned_install_detector.cc",
     "cloned_install_detector.h",
@@ skipping 339 matching lines @@
     ]
   }
 
   # iOS is not supported by the profiler and the ios-simulator bot chokes on
   # these tests.
   if (is_ios) {
     sources -= [ "child_call_stack_profile_collector_unittest.cc" ]
     deps -= [ "//components/metrics/public/cpp:call_stack_unit_tests" ]
   }
 }