MD History: increase contrast in synced tab promo flourish plant

chrome/browser/resources/md_history/synced_device_manager.html

 <link rel="import" href="chrome://resources/html/polymer.html">
 <link rel="import" href="chrome://resources/html/cr/ui/focus_grid.html">
 <link rel="import" href="chrome://resources/polymer/v1_0/iron-list/iron-list.html">
 <link rel="import" href="chrome://resources/polymer/v1_0/paper-button/paper-button.html">
 <link rel="import" href="chrome://resources/polymer/v1_0/paper-item/paper-item.html">
 <link rel="import" href="chrome://resources/cr_elements/cr_lazy_render/cr_lazy_render.html">
 <link rel="import" href="chrome://resources/cr_elements/cr_shared_menu/cr_shared_menu.html">
 <link rel="import" href="chrome://resources/cr_elements/shared_style_css.html">
 <link rel="import" href="chrome://history/shared_style.html">
 <link rel="import" href="chrome://history/synced_device_card.html">
 
 <dom-module id="history-synced-device-manager">
   <template>
     <style include="shared-style cr-shared-style">
       :host {
         display: block;
         overflow: auto;
       }
 
       #illustration {
         background: -webkit-image-set(
-            url(chrome://history/images/100/sign_in_promo.png) 1x,
-            url(chrome://history/images/200/sign_in_promo.png) 2x)
+            url(chrome://history/images/100/sign_in_promo.jpg) 1x,
+            url(chrome://history/images/200/sign_in_promo.jpg) 2x)
                 no-repeat center center;
         height: 222px;
         margin-top: 100px;
-        width: 594px;
+        width: 574px;
       }
 
       #no-synced-tabs {
         height: 100%;
       }
 
       #sign-in-guide {
         align-items: center;
         display: flex;
         flex-direction: column;
@@ skipping 60 matching lines @@
         </paper-item>
         <paper-item id="menuDeleteButton" class="menu-item"
             on-tap="onDeleteSessionTap_">
           $i18n{deleteSession}
         </paper-item>
       </cr-shared-menu>
     </template>
   </template>
   <script src="chrome://history/synced_device_manager.js"></script>
 </dom-module>