Pull ICU, rename component build GN variables.

third_party/libpng/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.
 
 config("libpng_config") {
   include_dirs = [ "." ]
 
   defines = [
     "CHROME_PNG_WRITE_SUPPORT",
     "PNG_USER_CONFIG",
   ]
 
   if (is_android) {
     #'toolsets': ['target', 'host'],
     defines += [ "CHROME_PNG_READ_PACK_SUPPORT" ]  # Required by freetype.
   }
 
   if (is_win) {
-    if (component_mode == "shared_library") {
+    if (is_component_build) {
       defines += [
         "PNG_USE_DLL",
         "PNG_NO_MODULEDEF",
       ]
     }
   }
 }
 
 source_set("libpng_sources") {
   sources = [
@@ skipping 49 matching lines @@
       ":libpng_sources",
     ]
   }
 } else {
   group("libpng") {
     public_deps = [
       ":libpng_sources",
     ]
   }
 }