Fix codemirror-editor build

Moves the polymer dependency out of the plugin and into the test, as it
is injected during the Gerrit build step (and bower install is not run
during the Gerrit //plugins:core build step).

Change-Id: I968bfc9ebd836e49c5c592222d032dec0fe4bc5c

gr-editor/gr-editor.html

diff --git a/gr-editor/gr-editor.html b/gr-editor/gr-editor.html
index f9c8869..fd8673e 100644
--- a/gr-editor/gr-editor.html
+++ b/gr-editor/gr-editor.html
@@ -14,8 +14,6 @@
 limitations under the License.
 -->
 
-<link rel="import" href="../bower_components/polymer/polymer.html">
-
 <link rel="import" href="gr-editor-styles.html">
 
 <script src="../bower_components/codemirror-minified/lib/codemirror.js"></script>

gr-editor/gr-editor_test.html

diff --git a/gr-editor/gr-editor_test.html b/gr-editor/gr-editor_test.html
index aa9a36e..2d68df6 100644
--- a/gr-editor/gr-editor_test.html
+++ b/gr-editor/gr-editor_test.html
@@ -19,6 +19,12 @@
 <meta name="viewport" content="width=device-width, minimum-scale=1.0, initial-scale=1.0, user-scalable=yes">
 <title>gr-editor</title>
 
+<!--
+Import polymer here, as the editor itself receives Polymer during Gerrit
+release build step.
+-->
+<link rel="import" href="../bower_components/polymer/polymer.html">
+
 <link rel="import" href="../bower_components/iron-test-helpers/iron-test-helpers.html">
 <link rel="import" href="gr-editor.html">
 <script src="../../../bower_components/webcomponentsjs/webcomponents-lite.min.js"></script>