Add optional legal text in email optin UI

Bug: b/109879970
Test: Manual Test
Change-Id: Ic13b02e3ad514bc8f5e1feb0e255bcd54f02ab4d
Reviewed-on: https://chromium-review.googlesource.com/1173391
Commit-Queue: Yue Li <updowndota@chromium.org>
Reviewed-by: Xiaohui Chen <xiaohuic@chromium.org>
Reviewed-by: Xiyuan Xia <xiyuan@chromium.org>
Cr-Commit-Position: refs/heads/master@{#583103}

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

@@ -5,3 +5,7 @@
 .title {
   padding: 32px 0 24px 0;
 }
+
+p {
+  margin-block-end: 0;
+}

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

@@ -107,6 +107,11 @@ Polymer({
       var description = document.createElement('div');
       description.className = 'zippy-description';
       description.textContent = data['description'];
+      if (data['legalText']) {
+        var legalText = document.createElement('p');
+        legalText.textContent = data['legalText'];
+        description.appendChild(legalText);
+      }
       zippy.appendChild(description);
 
       Polymer.dom(this.$['insertion-point']).appendChild(zippy);

chrome/browser/ui/webui/chromeos/assistant_optin/assistant_optin_handler.cc

@@ -142,6 +142,7 @@ base::Value CreateGetMoreData(bool email_optin_needed,
     data.SetKey("defaultEnabled",
                 base::Value(email_optin_ui.default_enabled()));
     data.SetKey("iconUri", base::Value(email_optin_ui.icon_uri()));
+    data.SetKey("legalText", base::Value(email_optin_ui.legal_text()));
     get_more_data.GetList().push_back(std::move(data));
   }
 

chromeos/services/assistant/public/proto/email_opt_in_ui.proto

@@ -18,6 +18,10 @@ message EmailOptInUi {
   // A paragraph telling the user what they get from email updates.
   optional string description = 3;
 
+  // Supplementary text that is only required in some locales which tells
+  // users how to opt out.
+  optional string legal_text = 4;
+
   // Whether the switch should default to enabled. This affects the opt-in
   // state if the user does not override it.
   optional bool default_enabled = 5;