WebUI: Cleanup unnecessary code duplication in cr_dialog.

At r819219 a large part of cr_dialog.html code was duplicated between
CrOS/non-CrOS builds unnecessarily.

Bug: 1007433
Change-Id: Ia7de207202cdbd39f0b8d8671cd809249da36081
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2565184
Commit-Queue: dpapad <dpapad@chromium.org>
Reviewed-by: Kyle Horimoto <khorimoto@chromium.org>
Cr-Commit-Position: refs/heads/master@{#831882}

ui/webui/resources/cr_elements/cr_dialog/cr_dialog.html

@@ -148,12 +148,14 @@
         margin-top: 4px;
       }
     </style>
-    <!-- TODO(crbug/1139958): Remove "not chromeos" block when chromeVox issue is fixed-->
-    <!--Update both "not chromeos" and "chromeos" blocks if either changes-->
-<if expr="not chromeos">
+    <!-- TODO(crbug/1139958): Remove "not chromeos" block when chromeVox issue
+        is fixed-->
     <dialog id="dialog" on-close="onNativeDialogClose_"
         on-cancel="onNativeDialogCancel_" part="dialog"
-        aria-labelledby="title">
+<if expr="not chromeos">
+        aria-labelledby="title"
+</if>
+        >
     <!-- This wrapper is necessary, such that the "pulse" animation is not
         erroneously played when the user clicks on the outer-most scrollbar. -->
       <div id="content-wrapper" part="wrapper">
@@ -175,32 +177,6 @@
         <slot name="footer"></slot>
       </div>
     </dialog>
-</if>
-<if expr="chromeos">
-    <dialog id="dialog" on-close="onNativeDialogClose_"
-        on-cancel="onNativeDialogCancel_" part="dialog">
-    <!-- This wrapper is necessary, such that the "pulse" animation is not
-        erroneously played when the user clicks on the outer-most scrollbar. -->
-        <div id="content-wrapper" part="wrapper">
-          <div class="top-container">
-            <div id="title" class="title-container" tabindex="-1">
-              <slot name="title"></slot>
-            </div>
-            <cr-icon-button id="close" class="icon-clear"
-                hidden$="[[!showCloseButton]]" aria-label$="[[closeText]]"
-                on-click="cancel" on-keypress="onCloseKeypress_">
-            </cr-icon-button>
-          </div>
-          <slot name="header"></slot>
-          <div class="body-container" id="container" show-bottom-shadow
-              part="body-container">
-            <slot name="body"></slot>
-          </div>
-          <slot name="button-container"></slot>
-          <slot name="footer"></slot>
-        </div>
-    </dialog>
-</if>
   </template>
   <script src="cr_dialog.js"></script>
 </dom-module>