Add keyboard auto-repeat metrics

Metrics already exist but were never added to the inputs.

R=stevenjb@chromium.org

Review URL: https://codereview.chromium.org/571233002

Cr-Commit-Position: refs/heads/master@{#294938}

chrome/browser/resources/options/chromeos/keyboard_overlay.html

@@ -103,7 +103,7 @@
           <span class="option-name" i18n-content="autoRepeatDelay"></span>
             <span i18n-content="autoRepeatDelayLong"></span>
             <input id="auto-repeat-delay-range" type="range"
-                class="touch-slider"
+                class="touch-slider" metric="Options_KeyboardAutoRepeat_Delay"
                 pref="settings.language.xkb_auto_repeat_delay_r2" dialog-pref>
             <span i18n-content="autoRepeatDelayShort"></span>
           </div>
@@ -113,7 +113,7 @@
             <input id="auto-repeat-interval-range" type="range"
                 class="touch-slider"
                 pref="settings.language.xkb_auto_repeat_interval_r2"
-                dialog-pref>
+                metric="Options_KeyboardAutoRepeat_Interval" dialog-pref>
             <span i18n-content="autoRepeatRateFast"></span>
           </div>
       </div>