Enable precompiled headers for Blink on Windows.

third_party/WebKit/Source/platform/heap/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")
 
 source_set("heap") {
   # This target is a logical part of the platform and only the platform target
   # should depend on it.
   visibility = [ "//third_party/WebKit/Source/platform" ]
@@ skipping 38 matching lines @@
     "ThreadingTraits.h",
     "TraceTraits.h",
     "Visitor.cpp",
     "Visitor.h",
     "WrapperVisitor.h",
   ]
 
   defines = [ "BLINK_PLATFORM_IMPLEMENTATION=1" ]
 
   configs += [
+    "//third_party/WebKit/Source:blink_pch",
     "//third_party/WebKit/Source:config",
     "//third_party/WebKit/Source:non_test_config",
     "//third_party/WebKit/Source:inside_blink",
     "//third_party/WebKit/Source:features",
     "//build/config/compiler:no_size_t_to_int_warning",
   ]
 
   deps = [
     "//base",
     "//third_party/WebKit/Source/platform:make_platform_generated",
@@ skipping 27 matching lines @@
     "//third_party/WebKit/Source/wtf",
   ]
   if (is_android) {
     deps += [
       "//base:base_java",
       "//content/shell/android:content_shell_assets",
       "//net/android:net_java",
     ]
   }
 }