Precompile Document.h and LayoutObject.h for Source/web

Source/build/win/precompile-core.gypi

+# Copyright 2015 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.
+
+# Include this file to make core targets in your .gyp use the default precompiled
+# header on Windows, when precompiled headers are turned on.
+
+{
+  'conditions': [
+      ['OS=="win" and chromium_win_pch==1', {
+          'target_defaults': {
+              'msvs_precompiled_header': '<(DEPTH)/third_party/WebKit/Source/build/win/Precompile-core.h',
+              'msvs_precompiled_source': '<(DEPTH)/third_party/WebKit/Source/build/win/Precompile-core.cpp',
+              'sources': ['<(DEPTH)/third_party/WebKit/Source/build/win/Precompile-core.cpp'],
+          }
+      }],
+  ],
+}