Assistant OptIn: Migrate templates from <content> to <slot>

Bug: b/78190629
Cq-Include-Trybots: luci.chromium.try:closure_compilation
Change-Id: I553fb8a9363775f3dfe110bef559f12c2e93db34
Reviewed-on: https://chromium-review.googlesource.com/1103614
Commit-Queue: Yue Li <updowndota@chromium.org>
Reviewed-by: Xiyuan Xia <xiyuan@chromium.org>
Cr-Commit-Position: refs/heads/master@{#568150}

chrome/browser/resources/chromeos/assistant_optin/assistant_get_more.html

@@ -9,7 +9,7 @@
     <link rel="stylesheet" href="assistant_get_more.css">
     <oobe-dialog id="get-more-dialog" role="dialog" has-buttons hide-shadow
         no-footer-padding no-header android>
-      <div class = "footer">
+      <div slot="footer">
         <div id="main-container">
           <iron-icon src="assistant_logo.png">
           </iron-icon>
@@ -17,7 +17,7 @@
           <div id="insertion-point"></div>
         </div>
       </div>
-      <div class="bottom-buttons flex layout horizontal">
+      <div slot="bottom-buttons" class="flex layout horizontal">
         <div class="flex"></div>
         <oobe-text-button id="next-button" inverse android on-tap="onNextTap_"
             disabled="[[buttonsDisabled]]" hidden="[[moreContents]]">

chrome/browser/resources/chromeos/assistant_optin/assistant_loading.html

@@ -11,7 +11,7 @@
     <link rel="stylesheet" href="assistant_loading.css">
     <oobe-dialog id="loading-dialog" role="dialog" has-buttons hide-shadow
         no-footer-padding no-header android>
-      <div class = "footer">
+      <div slot="footer">
         <div id="error-container">
           <div class="title"
             i18n-content="assistantOptinLoadErrorTitle"></div>
@@ -26,7 +26,7 @@
           <paper-progress class="slow" indeterminate></paper-progress>
         </div>
       </div>
-      <div class="bottom-buttons flex layout horizontal">
+      <div slot="bottom-buttons" class="flex layout horizontal">
         <div class="flex"></div>
         <oobe-text-button id="retry-button" inverse android
             on-tap="onRetryTap_" disabled="[[buttonsDisabled]]">

chrome/browser/resources/chromeos/assistant_optin/assistant_third_party.html

@@ -9,7 +9,7 @@
     <link rel="stylesheet" href="assistant_third_party.css">
     <oobe-dialog id="third-party-dialog" role="dialog" has-buttons hide-shadow
         no-footer-padding no-header android>
-      <div class = "footer">
+      <div slot="footer">
         <div id="main-container">
           <iron-icon src="assistant_logo.png">
           </iron-icon>
@@ -20,7 +20,7 @@
           </div>
         </div>
       </div>
-      <div class="bottom-buttons flex layout horizontal">
+      <div slot="bottom-buttons" class="flex layout horizontal">
         <div class="flex"></div>
         <oobe-text-button id="next-button" inverse android on-tap="onNextTap_"
             disabled="[[buttonsDisabled]]" hidden="[[moreContents]]">

chrome/browser/resources/chromeos/assistant_optin/assistant_value_prop.html

@@ -11,7 +11,7 @@
     <link rel="stylesheet" href="assistant_value_prop.css">
     <oobe-dialog id="value-prop-dialog" class="value-prop-loading"
         role="dialog" has-buttons no-footer-padding no-header android>
-      <div class = "footer">
+      <div slot="footer">
         <div id="view-container">
           <webview id="value-prop-view"></webview>
           <div class="line"></div>
@@ -26,7 +26,7 @@
           </div>
         </div>
       </div>
-      <div class="bottom-buttons flex layout horizontal">
+      <div slot="bottom-buttons" class="flex layout horizontal">
         <oobe-text-button id="skip-button" android on-tap="onSkipTap_"
             disabled="[[buttonsDisabled]]">
           <div id="skip-button-text"></div>