MD Settings: Tweak search bubble opacity and size.

chrome/browser/resources/settings/settings_shared_css.html

 <link rel="import" href="chrome://resources/cr_elements/shared_style_css.html">
 <link rel="import" href="settings_icons_css.html">
 <link rel="import" href="settings_vars_css.html">
 
 <!-- Common styles for Material Design settings. -->
 <dom-module id="settings-shared">
   <template>
     <style include="settings-icons cr-shared-style">
       /* Prevent action-links from being selected to avoid accidental
        * selection when trying to click it. */
@@ skipping 358 matching lines @@
       }
 
       .favicon-image {
         background-repeat: no-repeat;
         background-size: contain;
         height: 16px;
         width: 16px;
       }
 
       .search-bubble {
+        /* RGB value matches var(--paper-yellow-500). */
+        --search-bubble-color: rgba(255, 235, 59, 0.9);
         position: absolute;
         z-index: 1;
       }
 
       .search-bubble-innards {
         align-items: center;
-        background-color: var(--paper-yellow-500);
+        background-color: var(--search-bubble-color);
         border-radius: 2px;
+        max-width: 100px;
+        min-width: 64px;
         padding: 4px 10px;
         text-align: center;
-        width: 100px;
       }
 
       /* Provides the arrow which points at the anchor element. */
       .search-bubble-innards::after {
-        background-color: var(--paper-yellow-500);
+        background-color: var(--search-bubble-color);
         content: '';
         height: 10px;
-        left: 55px;
+        left: calc(50% - 5px);

[dschuyler, 2017/07/07 19:26:08]

Maybe: The width of a diamond with 10px sides is about 7.0711px or about a shift
of (50% - 3.5355px). Another option is to reduce the side length down from 10px.
Though not a big deal if showing part of the diamond looks good as-is. It's just
that more than half the diamond is tucked under. 

         position: absolute;
         top: -5px;
         transform: rotate(-45deg);
         width: 10px;
         z-index: -1;
       }
 
       /* Turns the arrow direction downwards, when the bubble is placed above
        * the anchor element */
       .search-bubble-innards.above::after {
         bottom: -5px;
         top: auto;
         transform: rotate(-135deg);
       }
 
       .column-header {
         color: var(--paper-grey-600);
         font-weight: 500;
       }
     </style>
   </template>
 </dom-module>