Convert component_mode -> is_component_build for GN

Source/wtf/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("//testing/test.gni")
 
 # The list of files is kept in the .gypi.
 gypi_values = exec_script("//build/gypi_to_gn.py",
                           [ rebase_path("wtf.gypi") ],
                           "scope",
@@ skipping 13 matching lines @@
     ]
 
     cflags = [
       # Don't complain about calling specific versions of templatized
       # functions (e.g. in RefPtrHashMap.h).
       "/wd4344",
       # dtoa, icu, etc. like doing assignment within conditional.
       "/wd4706",
     ]
 
-    if (component_mode == "shared_library") {
+    if (is_component_build) {
       # Chromium windows multi-dll build enables C++ exceptions and this causes
       # wtf to generate 4291 warning due to operator new/delete
       # implementations. Disable the warning for chromium windows multi-dll
       # build.
       cflags += [ "/wd4291" ]
     }
   }
 }
 
 component("wtf") {
@@ skipping 89 matching lines @@
     # TODO(jschuh): crbug.com/167187 fix size_t to int truncations.
     "//build/config/compiler:no_size_t_to_int_warning",
     "//third_party/WebKit/Source:config",
     "//third_party/WebKit/Source:non_test_config",
   ]
 
   deps = [
     ":wtf",
   ]
 }