Add a PartialPreReadImage function to file_util (on Windows).

chrome/chrome_exe.gypi

 # Copyright (c) 2012 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.
 
 {
   'targets': [
     {
       'target_name': 'chrome',
       'type': 'executable',
       'mac_bundle': 1,
@@ skipping 436 matching lines @@
             # Override the outer definition of CHROMIUM_STRIP_SAVE_FILE.
             'CHROMIUM_STRIP_SAVE_FILE': 'app/app_asan.saves',
           },
         }],
         ['OS=="win"', {
           'dependencies': [
             'chrome_dll',
             'chrome_version_resources',
             'installer_util',
             'installer_util_strings',
+            'image_pre_reader',
             '../base/base.gyp:base',
             '../breakpad/breakpad.gyp:breakpad_handler',
             '../breakpad/breakpad.gyp:breakpad_sender',
             '../sandbox/sandbox.gyp:sandbox',
             'app/policy/cloud_policy_codegen.gyp:policy',
           ],
           'sources': [
             'app/chrome_exe.rc',
             '<(SHARED_INTERMEDIATE_DIR)/chrome_version/chrome_exe_version.rc',
           ],
@@ skipping 36 matching lines @@
         ['OS=="win" and component=="shared_library"', {
           'defines': ['COMPILE_CONTENT_STATICALLY'],
         }]
       ],
     },
   ],
   'conditions': [
     ['OS=="win"', {
       'targets': [
         {
+          'target_name': 'image_pre_reader',
+          'type': 'static_library',
+          'sources': [
+            'app/image_pre_reader_win.cc',
+            'app/image_pre_reader_win.h',
+          ],
+          'dependencies': [
+             '../base/base.gyp:base',
+          ],
+        },
+        {
           'target_name': 'chrome_nacl_win64',
           'type': 'executable',
           'product_name': 'nacl64',
           'sources': [
             'app/breakpad_win.cc',
             'app/hard_error_handler_win.cc',
             'nacl/nacl_exe_win_64.cc',
             '../content/app/startup_helper_win.cc',
             '../content/common/debug_flags.cc',  # Needed for sandbox_policy.cc
             '../content/common/hi_res_timer_manager_win.cc',
@@ skipping 34 matching lines @@
           'configurations': {
             'Common_Base': {
               'msvs_target_platform': 'x64',
             },
           },
         },
       ],
     }],
   ],
 }