[MD History] Make forward/backward work in grouped mode.

chrome/browser/resources/md_history/history_toolbar.html

 <link rel="import" href="chrome://resources/html/polymer.html">
 <link rel="import" href="chrome://resources/polymer/v1_0/iron-icon/iron-icon.html">
 <link rel="import" href="chrome://resources/polymer/v1_0/paper-icon-button/paper-icon-button.html">
 <link rel="import" href="chrome://resources/cr_elements/icons.html">
 <link rel="import" href="chrome://resources/cr_elements/cr_lazy_render/cr_lazy_render.html">
 <link rel="import" href="chrome://resources/cr_elements/cr_toolbar/cr_toolbar.html">
 <link rel="import" href="chrome://history/browser_service.html">
 <link rel="import" href="chrome://history/icons.html">
 <link rel="import" href="chrome://history/shared_style.html">
 
@@ skipping 213 matching lines @@
     </div>
     <template is="dom-if" if="[[isGroupedMode]]">
       <div id="grouped-buttons-container">
         <paper-tabs attr-for-selected="value" selected="{{groupedRange}}"
             id="grouped-range-buttons">
           <paper-tab value="0">$i18n{rangeAllTime}</paper-tab>
           <paper-tab value="1">$i18n{rangeWeek}</paper-tab>
           <paper-tab value="2">$i18n{rangeMonth}</paper-tab>
         </paper-tabs>
         <div id="grouped-nav-container">
-          <span id="grouped-date">
+          <span id="grouped-date" hidden$="[[querying]]">

[tsergeant, 2016/11/11 02:34:27]

IMO, this hiding is unnecessary.

It just causes the date to flash in and out distractingly. Without it, the dates
for the old results should still display until the new results are ready. This
mirrors the behavior of the main view, where the old results show until the new
ones appear.

[calamity, 2016/11/22 06:44:56]

Done.

             {{getHistoryInterval_(queryStartTime, queryEndTime)}}
           </span>
-          <paper-icon-button icon="history:today" alt="$i18n{rangeToday}"
-              title="$i18n{rangeToday}"></paper-icon-button>
-          <paper-icon-button icon="history:chevron-left"
-              alt="$i18n{rangePrevious}" title="$i18n{rangePrevious}"
-              class="rtl-reversible"></paper-icon-button>
-          <paper-icon-button icon="cr:chevron-right"
-              alt="$i18n{rangeNext}" title="$i18n{rangeNext}"
-              class="rtl-reversible"></paper-icon-button>
+          <paper-icon-button id="today-button" icon="history:today"

[tsergeant, 2016/11/11 02:34:27]

Do these buttons actually need IDs?

[calamity, 2016/11/22 06:44:56]

Just for tests?

+              alt="$i18n{rangeToday}"
+              title="$i18n{rangeToday}"
+              on-tap="todayTapped_"

[tsergeant, 2016/11/11 02:34:27]

Nit: Follow naming style of onTodayTap_ here and below

[calamity, 2016/11/22 06:44:56]

Done.

+              disabled="[[isToday_(groupedOffset)]]"></paper-icon-button>
+          <paper-icon-button id="prev-button" icon="history:chevron-left"
+              alt="$i18n{rangePrevious}"
+              title="$i18n{rangePrevious}"
+              class="rtl-reversible"
+              on-tap="prevTapped_"
+              disabled="[[queryFinished]]"></paper-icon-button>
+          <paper-icon-button id="next-button" icon="cr:chevron-right"
+              alt="$i18n{rangeNext}"
+              title="$i18n{rangeNext}"
+              class="rtl-reversible"
+              on-tap="nextTapped_"
+              disabled="[[isToday_(groupedOffset)]]"></paper-icon-button>
         </div>
       </div>
     </template>
   </template>
   <script src="chrome://history/history_toolbar.js"></script>
 </dom-module>