Add //ipc to "gn check", work on base

.gn

Index: .gn
diff --git a/.gn b/.gn
index 23013d4f9d0682c6784c5ad86998e32151467bcf..1429a87ac7628e0abb0596a84a86ff947aea1acf 100644
--- a/.gn
+++ b/.gn
@@ -14,4 +14,11 @@ secondary_source = "//build/secondary/"
 # matching these patterns (see "gn help label_pattern" for format) will have
 # their includes checked for proper dependencies when you run either
 # "gn check" or "gn gen --check".
-check_targets = [ "//cc/*" ]
+check_targets = [
+  # Requires GN binary >= 314794 and to mark the "...__generate_enum" action in
+  # build/config/android/rules.gni "java_cpp_enum" template with
+  #   check_includes = false.
+  #"//base/*",
+  "//cc/*",
+  "//ipc/*",
+]