crostini: UI fixes for disk resizing in settings.

* Add a margin around the slider so the label doesn't get cut off and no
  scrollbar shows up
* Align the max label correctly under the slider

Screenshot: https://drive.google.com/open?id=1-K52YfP_4ZQ-zKkIu2ErLrprJXQM7kGY

Bug: chromium:858815
Test: Manual
Change-Id: I8c5b054a1df920f832e652aaa0848cd752601159
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2115868
Commit-Queue: David Munro <davidmunro@google.com>
Auto-Submit: David Munro <davidmunro@google.com>
Reviewed-by: Kyle Horimoto <khorimoto@chromium.org>
Cr-Commit-Position: refs/heads/master@{#753073}

chrome/browser/resources/settings/chromeos/crostini_page/crostini_disk_resize_dialog.html

@@ -8,23 +8,20 @@
 <link rel="import" href="crostini_browser_proxy.html">
 <link rel="import" href="../../i18n_setup.html">
 <link rel="import" href="../../settings_shared_css.html">
-
-<style>
-  #labels {
-    display: flex;
-    flex-direction: row;
-    justify-content: space-between;
-  }
-
-  #resize-block {
-    align-items: stretch;
-    display: flex;
-    flex-direction: column;
-  }
-</style>
 <dom-module id="settings-crostini-disk-resize-dialog">
   <template>
-    <style include="settings-shared"></style>
+    <style include="settings-shared">
+      #disk-labels {
+        display: flex;
+        justify-content: space-between;
+      }
+
+      #resize-block {
+        align-items: stretch;
+        margin-inline-end: 10px;
+        margin-inline-start: 10px;
+      }
+    </style>
     <cr-dialog id="diskResizeDialog" close-text="$i18n{close}">
       <div slot="title">$i18n{crostiniDiskResizeTitle}</div>
       <div slot="body">
@@ -34,7 +31,7 @@
                 value="[[defaultDiskSizeTick_]]" ticks="[[diskSizeTicks_]]"
                 disabled="[[resizing_]]">
             </cr-slider>
-            <div id="labels">
+            <div id="disk-labels">
               <div id="label-begin">[[minDiskSize_]]</div>
               <div id="label-end">[[maxDiskSize_]]</div>
             </div>