Revert of clang/win: Disable precompiled headers.

build/win_precompile.gypi

 # Copyright (c) 2011 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 targets in your .gyp use the default
 # precompiled header on Windows, in debug builds only as the official
 # builders blow up (out of memory) if precompiled headers are used for
 # release builds.
 
 {
   'conditions': [
-    # TODO(thakis): Reenable on clang after https://crbug.com/605570 is fixed.
-    ['OS=="win" and chromium_win_pch==1 and clang==0', {
+    ['OS=="win" and chromium_win_pch==1', {
         'target_defaults': {
           'msvs_precompiled_header': 'build/precompile.h',
           'msvs_precompiled_source': '<(DEPTH)/build/precompile.cc',
           'sources': ['<(DEPTH)/build/precompile.cc'],
           'include_dirs': [ '<(DEPTH)' ],
         }
     }],
   ],
 }