Convert component_mode -> is_component_build for GN

Source/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.
 
 import("config.gni")
 if (is_clang) {
   import("//build/config/clang/clang.gni")
 }
 
 visibility = [ "//third_party/WebKit/*" ]
@@ skipping 25 matching lines @@
     cflags += [
       "/wd4305",  # Truncation from 'type1' to 'type2'.
       "/wd4324",  # Struct padded due to declspec(align).
       "/wd4714",  # Function marked forceinline not inlined.
       "/wd4800",  # Value forced to bool.
       "/wd4996",  # Deprecated function call.
     ]
   }
 
   if (is_win) {
-    if (component_mode == "shared_library") {
+    if (is_component_build) {
       defines += [ "USING_V8_SHARED" ]
     }
   } else {  # ! Windows
     # TODO(GYP) this should be based on gcc_version >= 46 but GN doesn't have a
     # concept of GCC version yet.
 
     # Disable warnings about c++0x compatibility, as some names (such as
     # nullptr) conflict with upcoming c++0x types.
     cflags_cc = [ "-Wno-c++0x-compat" ]
   }
@@ skipping 19 matching lines @@
 
 # The follow configs apply to all targets except for unit tests, which rely on
 # static initializers.
 config("non_test_config") {
   cflags = []
 
   if (is_clang) {
     cflags += [ "-Wglobal-constructors" ]
   }
 }