Switch ChromeOS Chromium login to use IJG libjpeg

build/common.gypi

Index: build/common.gypi
diff --git a/build/common.gypi b/build/common.gypi
index d00b6a70826b131ca5f16cea034b2ede8823d8df..67b973e9cc0de18eb8b54152822cd9fcba5ac4a2 100644
--- a/build/common.gypi
+++ b/build/common.gypi
@@ -889,11 +889,6 @@
           'use_canvas_skia%': 1,
         }],
 
-        ['chromeos==1', {
-          # When building for ChromeOS we dont want Chromium to use libjpeg_turbo.
-          'use_libjpeg_turbo%': 0,
-        }],
-
         # Do not enable the Settings App on ChromeOS.
         ['enable_app_list==1 and chromeos==0', {
           'enable_settings_app%': 1,
@@ -1505,6 +1500,11 @@
     # ChromeVox, which can then be enabled via a command-line switch.
     'use_chromevox_next%': 0,
 
+    # Used to set libjpeg_gyp_path. Chrome OS ui/gfx/gfx.gyp uses the IJG path
+    # for robust login screen decoding.
+    'libjpeg_ijg_gyp_path': '../third_party/libjpeg/libjpeg.gyp',
+    'libjpeg_turbo_gyp_path': '../third_party/libjpeg_turbo/libjpeg.gyp',
+
     'conditions': [
       # Enable the Syzygy optimization step for the official builds.
       ['OS=="win" and buildtype=="Official" and syzyasan!=1', {
@@ -1991,9 +1991,9 @@
       # library used by Chromium.
       ['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': '<(libjpeg_ijg_gyp_path)',
       }, {
-        'libjpeg_gyp_path': '../third_party/libjpeg_turbo/libjpeg.gyp',
+        'libjpeg_gyp_path': '<(libjpeg_turbo_gyp_path)',
       }],
 
       # Options controlling the use of GConf (the classic GNOME configuration
@@ -2591,7 +2591,9 @@
       ['use_default_render_theme==1', {
         'defines': ['USE_DEFAULT_RENDER_THEME=1'],
       }],
-      ['use_libjpeg_turbo==1', {
+      ['use_libjpeg_turbo==1 and chromeos!=1', {
+        # Only used by ui/gfx/codec/jpeg_codec.cc. Chrome OS requires IJG for
+        # robustly decoding login screen images.
         'defines': ['USE_LIBJPEG_TURBO=1'],
       }],
       ['use_x11==1', {