Add an include-paths only jpeg group

third_party/BUILD.gn

 # Copyright 2014 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.
 
 if (is_android) {
   import("//build/config/android/config.gni")
 }
 
 assert(!is_ios, "This is not used on iOS, don't drag it in unintentionally")
 
@@ skipping 25 matching lines @@
     public_deps = [
       "//third_party/libjpeg_turbo:libjpeg",
     ]
     public_configs = [ ":libjpeg_turbo_config" ]
   } else {
     public_deps = [
       "//third_party/libjpeg:libjpeg",
     ]
   }
 }
+
+# This is a meta target that forwards include paths only to the system's
+# libjpeg, third_party/libjpeg, or third_party/libjpeg_turbo depending on the
+# build args declared in this file. This is needed, rarely, for targets that
+# need to reference libjpeg without explicitly building it.
+group("jpeg_includes") {
+  if (use_system_libjpeg) {
+    public_configs = [ ":system_libjpeg_config" ]
+  } else if (use_libjpeg_turbo) {
+    public_configs = [ "//third_party/libjpeg_turbo:libjpeg_config" ]
+  } else {
+    public_configs = [ "//third_party/libjpeg:libjpeg_config" ]
+  }
+}