WebView: prepare to depend on individual GMS services

build/config/android/config.gni

Index: build/config/android/config.gni
diff --git a/build/config/android/config.gni b/build/config/android/config.gni
index 8bfcf5b61434c64e21b39c30685baae7de631dab..2f68c894eb1b36f3f1f0ded5911fbdef497b3e67 100644
--- a/build/config/android/config.gni
+++ b/build/config/android/config.gni
@@ -56,16 +56,24 @@ if (is_android) {
     default_android_keystore_password = "chromium"
   }
 
+  # TODO(paulmiller): Remove; superseded by google_play_services_package.
   if (!defined(google_play_services_library)) {
     google_play_services_library =
         "//third_party/android_tools:google_play_services_default_java"
   }
 
+  # TODO(paulmiller): Remove; superseded by google_play_services_package.
   if (!defined(google_play_services_resources)) {
     google_play_services_resources =
         "//third_party/android_tools:google_play_services_default_resources"
   }
 
+  # google_play_services_package contains the path where individual client
+  # targets (e.g. google_play_services_base_java) are located.
+  if (!defined(google_play_services_package)) {
+    google_play_services_package = "//third_party/android_tools"
+  }
+
   webview_public_framework_jar =
       "//third_party/android_platform/webview/frameworks_7.0.0_r1.jar"
   if (!defined(webview_framework_jar)) {