Enable precompiled headers for Blink on Windows

third_party/WebKit/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.
 
 assert(!is_ios)
 
 import("//testing/test.gni")
 import("//third_party/WebKit/Source/config.gni")
 
 # The list of files is kept in the .gypi.
@@ skipping 32 matching lines @@
       # build.
       cflags += [ "/wd4291" ]
     }
   }
 }
 
 component("wtf") {
   sources = gypi_values.wtf_files
 
   configs += [
+    "//third_party/WebKit/Source:blink_pch",
     "//third_party/WebKit/Source:config",
     "//third_party/WebKit/Source:non_test_config",
   ]
 
   defines = [ "WTF_IMPLEMENTATION=1" ]
 
   public_configs = [
     ":wtf_config",
 
     # TODO(jschuh): crbug.com/167187 fix size_t to int truncations.
@@ skipping 51 matching lines @@
 
   sources += [ "testing/RunAllTests.cpp" ]
 
   # TODO(jschuh): crbug.com/167187 fix size_t to int truncations.
   configs += [ "//build/config/compiler:no_size_t_to_int_warning" ]
 
   if (is_win) {
     cflags = [ "/wd4068" ]  # Unknown pragma.
   }
 
-  configs += [ "//third_party/WebKit/Source:config" ]
+  configs += [
+    "//third_party/WebKit/Source:blink_pch",
+    "//third_party/WebKit/Source:config",
+  ]
 
   deps = [
     ":wtf",
     "//base",
     "//base/test:test_support",
     "//testing/gmock",
     "//testing/gtest",
   ]
 }