Clean up gyp settings for libjpeg

build/common.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.
 
 # IMPORTANT:
 # Please don't directly include this file if you are building via gyp_chromium,
 # since gyp_chromium is automatically forcing its inclusion.
 {
   # Variables expected to be overriden on the GYP command line (-D) or by
   # ~/.gyp/include.gypi.
@@ skipping 165 matching lines @@
 
       # The system libdir used for this ABI.
       'system_libdir%': 'lib',
 
       # On Linux, we build with sse2 for Chromium builds.
       'disable_sse2%': 0,
 
       # Use libjpeg-turbo as the JPEG codec used by Chromium.
       'use_libjpeg_turbo%': 1,
 
+      # Use system libjpeg. Note that the system's libjepg will be used even if
+      # use_libjpeg_turbo is set.
+      'use_system_libjpeg%': 0,
+
       # Variable 'component' is for cases where we would like to build some
       # components as dynamic shared libraries but still need variable
       # 'library' for static libraries.
       # By default, component is set to whatever library is set to and
       # it can be overriden by the GYP command line or by ~/.gyp/include.gypi.
       'component%': 'static_library',
 
       # Set to select the Title Case versions of strings in GRD files.
       'use_titlecase_in_grd_files%': 0,
 
@@ skipping 855 matching lines @@
 
       # Native Client glibc toolchain is enabled by default except on arm.
       ['target_arch=="arm"', {
         'disable_glibc%': 1,
       }, {
         'disable_glibc%': 0,
       }],
 
       # Set the relative path from this file to the GYP file of the JPEG
       # library used by Chromium.
-      ['use_libjpeg_turbo==1', {
+      ['use_system_libjpeg==1 or use_libjpeg_turbo==0', {
+        # Configuration for using the system libjeg is here.
+        'libjpeg_gyp_path': '../third_party/libjpeg/libjpeg.gyp',
+      }, {
         'libjpeg_gyp_path': '../third_party/libjpeg_turbo/libjpeg.gyp',
-      }, {
-        'libjpeg_gyp_path': '../third_party/libjpeg/libjpeg.gyp',
-      }],  # use_libjpeg_turbo==1
+      }],
 
       # Options controlling the use of GConf (the classic GNOME configuration
       # system) and GIO, which contains GSettings (the new GNOME config system).
       ['chromeos==1', {
         'use_gconf%': 0,
         'use_gio%': 0,
       }, {
         'use_gconf%': 1,
         'use_gio%': 1,
       }],
@@ skipping 2214 matching lines @@
     # settings in target dicts.  SYMROOT is a special case, because many other
     # Xcode variables depend on it, including variables such as
     # PROJECT_DERIVED_FILE_DIR.  When a source group corresponding to something
     # like PROJECT_DERIVED_FILE_DIR is added to a project, in order for the
     # files to appear (when present) in the UI as actual files and not red
     # red "missing file" proxies, the correct path to PROJECT_DERIVED_FILE_DIR,
     # and therefore SYMROOT, needs to be set at the project level.
     'SYMROOT': '<(DEPTH)/xcodebuild',
   },
 }