Separating theme from layout for CSS files.

Change-Id: I4c3cec28b30de8026df4298f65ebf6ad92faf68f
(cherry picked from commit 11f662f)
diff --git a/web/gui/src/main/webapp/app/fw/layer/dialog-theme.css b/web/gui/src/main/webapp/app/fw/layer/dialog-theme.css
new file mode 100644
index 0000000..bda182e
--- /dev/null
+++ b/web/gui/src/main/webapp/app/fw/layer/dialog-theme.css
@@ -0,0 +1,32 @@
+/*
+ * Copyright 2016-present Open Networking Laboratory
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+/*
+ ONOS GUI -- Dialog Service (theme) -- CSS file
+ */
+
+.light .dialog h2 {
+    color: black;
+}
+.dark .dialog h2 {
+    color: #ddd;
+}
+
+.dialog .dialog-button {
+    /* color works for both light and dark themes */
+    background-color: #c55;
+    color: white;
+}