Isolate gin_unittests and add them to bots

gin/BUILD.gn

Index: gin/BUILD.gn
diff --git a/gin/BUILD.gn b/gin/BUILD.gn
index 0b270c5894aa24aa21c286282d74b3adc8941d1f..02ba6f7df3c9e57727e3ba971bc996f4afa6ae42 100644
--- a/gin/BUILD.gn
+++ b/gin/BUILD.gn
@@ -177,8 +177,18 @@ test("gin_unittests") {
   ]
 
   deps = [
+    ":gin_shell",
     ":gin_test",
     "//base/test:test_support",
     "//v8",
   ]
 }
+
+# TODO(GYP): Delete this after we've converted everything to GN.
+# The _run targets exist only for compatibility w/ GYP.
+group("gin_unittests_run") {
+  testonly = true
+  deps = [
+    ":gin_unittests",
+  ]
+}