Enable resolution slider in tablet mode

Bug: 791199
Cq-Include-Trybots: master.tryserver.chromium.linux:closure_compilation
Change-Id: I22cfd969f415d32a5bd2aa135e610a55ddab857c
Reviewed-on: https://chromium-review.googlesource.com/804939Reviewed-by: Steven Bennetts <stevenjb@chromium.org>
Commit-Queue: Weidong Guo <weidongg@chromium.org>
Cr-Commit-Position: refs/heads/master@{#521400}

chrome/browser/resources/settings/device_page/display.html

@@ -147,7 +147,7 @@
             [[getResolutionText_(selectedDisplay, selectedModePref_.value)]]
           </div>
         </div>
-        <settings-slider disabled="[[selectedDisplay.isTabletMode]]"
+        <settings-slider disabled="[[!enableSetResolution_(selectedDisplay)]]"
             tick-values="[[modeValues_]]" pref="{{selectedModePref_}}"
             on-change="onSelectedModeChange_">
         </settings-slider>