MD Settings: fix input label floating around for search field.

chrome/browser/resources/settings/settings_page/settings_subpage_search.html

 <link rel="import" href="chrome://resources/cr_elements/cr_search_field/cr_search_field_behavior.html">
 <link rel="import" href="chrome://resources/cr_elements/icons.html">
 <link rel="import" href="chrome://resources/html/polymer.html">
 <link rel="import" href="chrome://resources/polymer/v1_0/iron-icon/iron-icon.html">
 <link rel="import" href="chrome://resources/polymer/v1_0/paper-icon-button/paper-icon-button.html">
 <link rel="import" href="chrome://resources/polymer/v1_0/paper-input/paper-input-container.html">
 
 <dom-module id="settings-subpage-search">
   <template>
     <style>
       :host {
         --subpage-search-underline: {
           margin-bottom: -2px;
           margin-top: -2px;
         }
       }
 
       :host {
         --paper-input-container-underline: var(--subpage-search-underline);
         --paper-input-container-underline-focus:
             var(--subpage-search-underline);
         --paper-input-container-underline-disabled:
             var(--subpage-search-underline);
         --paper-input-suffix: {
           /* Required to align the icon in |clearSearch| vertically. */
           line-height: 0;
         };
-
-        /**
-         * Kind of suck to have to hardcode these, but its necessary to
-         * make sure the conditional clear-icon will fit within input's height.
-         */
-        --paper-input-container-input: {
-          line-height: 24px;
-        };
-        --paper-input-container-label: {
-          line-height: 24px;
-        };
       }
 
       paper-icon-button {
         /* A 16px icon that fits on the input line. */
         height: 24px;
         padding: 4px;
         width: 24px;
       }
 
       #searchIcon {
         height: 16px;
         padding: 4px;
         vertical-align: middle;
         width: 16px;
       }
 
       paper-input-container {
         display: inline-block;
         vertical-align: middle;
         width: 160px;  /* Special width for search input. */
       }
 
       input[type='search']::-webkit-search-cancel-button {
         -webkit-appearance: none;
       }
 
-      #prompt,
       #searchInput {
         font-size: 92.3076923%;  /* To 12px from 13px. */
-      }
-
-      #prompt {
-        color: var(--paper-grey-600);
-      }
-
-      :host([has-search-text]) #prompt {
-        visibility: hidden;
+        min-height: 24px;
       }
 
       #searchInput {
         color: var(--paper-grey-800);
       }
 
       #clearSearch {
         -webkit-margin-end: -4px;
         -webkit-margin-start: 4px;
       }
     </style>
     <iron-icon id="searchIcon" icon="cr:search"></iron-icon>
     <paper-input-container no-label-float>
-      <label id="prompt">[[label]]</label>
       <input id="searchInput" type="search" on-search="onSearchTermSearch"
           on-input="onSearchTermInput" aria-labelledby="prompt" incremental
-          autofocus$="[[autofocus]]">
+          autofocus$="[[autofocus]]" placeholder="[[label]]">
       <paper-icon-button suffix icon="cr:cancel" id="clearSearch"
           on-tap="onTapClear_" title="[[clearLabel]]"
           hidden$="[[!hasSearchText]]">
       </paper-icon-button>
     </paper-input-container>
   </template>
   <script src="settings_subpage_search.js"></script>
 </dom-module>