Move gn _run target generation into test().

extensions/BUILD.gn

Index: extensions/BUILD.gn
diff --git a/extensions/BUILD.gn b/extensions/BUILD.gn
index e3600d8ff6e2a8ed6994d30f60e34cd7b19ae24a..a624a4529ab99ec7ac76549811e806010b308bd2 100644
--- a/extensions/BUILD.gn
+++ b/extensions/BUILD.gn
@@ -141,15 +141,6 @@ repack("shell_and_test_pak") {
   ]
 }
 
-# TODO(GYP): Delete this after we've converted everything to GN.
-# The _run targets exist only for compatibility w/ GYP.
-group("extensions_unittests_run") {
-  testonly = true
-  deps = [
-    ":extensions_unittests",
-  ]
-}
-
 test("extensions_unittests") {
   sources =
       rebase_path(extensions_tests_gypi_values.extensions_unittests_sources,
@@ -218,15 +209,6 @@ test("extensions_unittests") {
   }
 }
 
-# TODO(GYP): Delete this after we've converted everything to GN.
-# The _run targets exist only for compatibility w/ GYP.
-group("extensions_browsertests_run") {
-  testonly = true
-  deps = [
-    ":extensions_browsertests",
-  ]
-}
-
 test("extensions_browsertests") {
   sources =
       rebase_path(extensions_tests_gypi_values.extensions_browsertests_sources,