Refactor //ios:all target in preparation of upstreaming.

ios/chrome/app/BUILD.gn

Index: ios/chrome/app/BUILD.gn
diff --git a/ios/chrome/app/BUILD.gn b/ios/chrome/app/BUILD.gn
index 8f522fcaa997c323aeac7d1925660ac46cb4d85c..aba8cac529fc055b0bf1b7b5906f841e69b4dc3c 100644
--- a/ios/chrome/app/BUILD.gn
+++ b/ios/chrome/app/BUILD.gn
@@ -7,6 +7,18 @@ import("//build/mac/tweak_info_plist.gni")
 import("//ios/build/chrome_build.gni")
 import("//ios/public/provider/chrome/browser/build_config.gni")
 
+# This empty target is there to help with upstreaming by removing a manual
+# step from the process (updating the //ios:all target). It will be changed
+# to a real target as part of upstreaming.
+group("chrome") {
+}
+
+# This empty target is there to help with upstreaming by removing a manual
+# step from the process (updating the //ios:all target). It will be changed
+# to a real target as part of upstreaming.
+group("chrome_clean_skeleton") {
+}
+
 source_set("app") {
   sources = [
     "deferred_initialization_runner.h",