MD History: Fix ripple styling caused by paper-icon-button update.

Bug: 832012
Cq-Include-Trybots: master.tryserver.chromium.linux:closure_compilation
Change-Id: I3c1b7499de7085f1ca109748b28b5067754b5aaa
Reviewed-on: https://chromium-review.googlesource.com/1010481Reviewed-by: Demetrios Papadopoulos <dpapad@chromium.org>
Commit-Queue: Hector Carmona <hcarmona@chromium.org>
Cr-Commit-Position: refs/heads/master@{#550442}

ui/webui/resources/cr_elements/cr_toolbar/cr_toolbar_selection_overlay.html

 <link rel="import" href="chrome://resources/html/polymer.html">
+<link rel="import" href="chrome://resources/cr_elements/cr_icons_css.html">
 <link rel="import" href="chrome://resources/cr_elements/icons.html">
 <link rel="import" href="chrome://resources/polymer/v1_0/paper-button/paper-button.html">
 <link rel="import" href="chrome://resources/polymer/v1_0/paper-icon-button/paper-icon-button-light.html">
 
 <dom-module id="cr-toolbar-selection-overlay">
   <template>
-    <style>
+    <style include="cr-icons">
       :host {
         -webkit-padding-start: var(--cr-toolbar-field-margin, 0);
         display: flex;
@@ -35,7 +36,7 @@
         flex: 1;
       }
 
-      button {
+      paper-icon-button-light {
         -webkit-margin-end: 24px;
         -webkit-margin-start: 2px;
         height: 36px;