Pull ICU, rename component build GN variables.

build/config/BUILDCONFIG.gn

 # Copyright (c) 2013 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.
 
 # =============================================================================
 # PLATFORM SELECTION
 # =============================================================================
 #
 # There are two main things to set: "os" and "cpu". The "toolchain" is the name
 # of the GN thing that encodes combinations of these things.
@@ skipping 586 matching lines @@
   # on multiple platforms, but this whole block of code (how we define
   # host_toolchain) needs to be reworked regardless to key off of host_os
   # and host_cpu rather than the is_* variables.
   host_toolchain = "//build/toolchain/linux:clang_x64"
 }
 
 # ==============================================================================
 # COMPONENT SETUP
 # ==============================================================================
 
-# TODO(brettw): Convert component_mode to being a non-exported variable
-# ("_component_mode" instead) once ICU's BUILD.gn file is updated to use
-# is_component_build instead.
 if (is_component_build) {
-  component_mode = "shared_library"
+  _component_mode = "shared_library"
 } else {
-  component_mode = "source_set"
+  _component_mode = "source_set"
 }
-
 template("component") {
-  target(component_mode, target_name) {
+  target(_component_mode, target_name) {
     forward_variables_from(invoker, "*")
 
     # All shared libraries must have the sanitizer deps to properly link in
     # asan mode (this target will be empty in other cases).
     if (!defined(deps)) {
       deps = []
     }
     deps += [ "//build/config/sanitizers:deps" ]
   }
 }