MD Extensions: fix some CSS nits in options_dialog.html

* Alpabetize variables and mixins
* Remove ; after mixins (unneeded)
* --scroll-border: none; is more correcter (applied in border: rule)

R=rdevlin.cronin@chromium.org
BUG=none

Change-Id: I8007b227a759e517faf0113f3d6fa3a5e2b2ceff
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1559654
Commit-Queue: Devlin <rdevlin.cronin@chromium.org>
Reviewed-by: Devlin <rdevlin.cronin@chromium.org>
Auto-Submit: Dan Beam <dbeam@chromium.org>
Cr-Commit-Position: refs/heads/master@{#649177}

chrome/browser/resources/md_extensions/options_dialog.html

@@ -27,29 +27,19 @@
       }
 
       cr-dialog {
-        --scroll-border: 0;
         --cr-dialog-body: {
           height: 100%;
           padding-bottom: 0;
           padding-inline-end: 0;
           padding-inline-start: 0;
           padding-top: 0;
-        };
-
-        --cr-dialog-wrapper: {
-          height: 100%;
-          max-height: initial;
-          overflow: hidden;
-        };
-
+        }
+        --cr-dialog-body-border-bottom: none;
+        --cr-dialog-body-border-top: none;
         --cr-dialog-body-container: {
           height: 100%;
           min-height: initial;
-        };
-
-        --cr-dialog-body-border-bottom: none;
-        --cr-dialog-body-border-top: none;
-
+        }
         --cr-dialog-native: {
           opacity: 0;
           /* When loading, it's possible for an size update to follow after the
@@ -57,7 +47,13 @@
              A 100ms delay for the opacity transition will allow two updates to
              occur without showing the dialog resizing to the user. */
           transition: opacity 100ms ease 100ms;
-        };
+        }
+        --cr-dialog-wrapper: {
+          height: 100%;
+          max-height: initial;
+          overflow: hidden;
+        }
+        --scroll-border: none;
       }
     </style>