Add gr-icons to polygerrit

This follows the same pattern for icons as iron-icons, in which an icon
group is defiened via iron-iconset-svg and can be used like:

<link rel="import" href="../../shared/gr-icons/gr-icons.html">

<iron-icon icon="icons:unified"></iron-icon>

Change-Id: I4cc8ca06f93b1d9026e940d9b5967b000171afbc

polygerrit-ui/app/elements/shared/gr-icons/gr-icons.html

@@ -0,0 +1,30 @@
+<!--
+Copyright (C) 2017 The Android Open Source Project
+
+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.
+-->
+<link rel="import" href="../../../bower_components/iron-icon/iron-icon.html">
+<link rel="import" href="../../../bower_components/iron-iconset-svg/iron-iconset-svg.html">
+
+<iron-iconset-svg name="gr-icons" size="24">
+  <svg>
+    <defs>
+      <!-- This SVG is a copy from iron-icons https://github.com/PolymerElements/iron-icons/blob/master/iron-icons.html -->
+      <g id="settings"><path d="M19.43 12.98c.04-.32.07-.64.07-.98s-.03-.66-.07-.98l2.11-1.65c.19-.15.24-.42.12-.64l-2-3.46c-.12-.22-.39-.3-.61-.22l-2.49 1c-.52-.4-1.08-.73-1.69-.98l-.38-2.65C14.46 2.18 14.25 2 14 2h-4c-.25 0-.46.18-.49.42l-.38 2.65c-.61.25-1.17.59-1.69.98l-2.49-1c-.23-.09-.49 0-.61.22l-2 3.46c-.13.22-.07.49.12.64l2.11 1.65c-.04.32-.07.65-.07.98s.03.66.07.98l-2.11 1.65c-.19.15-.24.42-.12.64l2 3.46c.12.22.39.3.61.22l2.49-1c.52.4 1.08.73 1.69.98l.38 2.65c.03.24.24.42.49.42h4c.25 0 .46-.18.49-.42l.38-2.65c.61-.25 1.17-.59 1.69-.98l2.49 1c.23.09.49 0 .61-.22l2-3.46c.12-.22.07-.49-.12-.64l-2.11-1.65zM12 15.5c-1.93 0-3.5-1.57-3.5-3.5s1.57-3.5 3.5-3.5 3.5 1.57 3.5 3.5-1.57 3.5-3.5 3.5z"/></g>
+      <!-- This is a custom PolyGerrit SVG -->
+      <g id="side-by-side"><path d="M17.1578947,10.8888889 L2.84210526,10.8888889 C2.37894737,10.8888889 2,11.2888889 2,11.7777778 L2,17.1111111 C2,17.6 2.37894737,18 2.84210526,18 L17.1578947,18 C17.6210526,18 18,17.6 18,17.1111111 L18,11.7777778 C18,11.2888889 17.6210526,10.8888889 17.1578947,10.8888889 Z M17.1578947,2 L2.84210526,2 C2.37894737,2 2,2.4 2,2.88888889 L2,8.22222222 C2,8.71111111 2.37894737,9.11111111 2.84210526,9.11111111 L17.1578947,9.11111111 C17.6210526,9.11111111 18,8.71111111 18,8.22222222 L18,2.88888889 C18,2.4 17.6210526,2 17.1578947,2 Z M16.1973628,2 L2.78874238,2 C2.35493407,2 2,2.4 2,2.88888889 L2,8.22222222 C2,8.71111111 2.35493407,9.11111111 2.78874238,9.11111111 L16.1973628,9.11111111 C16.6311711,9.11111111 16.9861052,8.71111111 16.9861052,8.22222222 L16.9861052,2.88888889 C16.9861052,2.4 16.6311711,2 16.1973628,2 Z" id="Shape" transform="scale(1.2) translate(10.000000, 10.000000) rotate(-90.000000) translate(-10.000000, -10.000000)"/></g>
+      <!-- This is a custom PolyGerrit SVG -->
+      <g id="unified"><path d="M4,2 L17,2 C18.1045695,2 19,2.8954305 19,4 L19,16 C19,17.1045695 18.1045695,18 17,18 L4,18 C2.8954305,18 2,17.1045695 2,16 L2,4 L2,4 C2,2.8954305 2.8954305,2 4,2 L4,2 Z M4,7 L4,9 L17,9 L17,7 L4,7 Z M4,11 L4,13 L17,13 L17,11 L4,11 Z" id="Combined-Shape" transform="scale(1.2)"/></g>
+    </defs>
+  </svg>
+</iron-iconset-svg>

polygerrit-ui/app/styles/shared-styles.html

@@ -78,6 +78,11 @@ limitations under the License.
         font-size: 1.17em;
         font-family: var(--font-family-bold);
       }
+      iron-icon {
+        color: #757575;
+        --iron-icon-height: 20px;
+        --iron-icon-width: 20px;
+      }
       /* Stopgap solution until we remove hidden$ attributes. */
       [hidden] {
         display: none !important;