Make update over cellular an option for user

chrome/browser/resources/settings/about_page/about_page_browser_proxy.js

Index: chrome/browser/resources/settings/about_page/about_page_browser_proxy.js
diff --git a/chrome/browser/resources/settings/about_page/about_page_browser_proxy.js b/chrome/browser/resources/settings/about_page/about_page_browser_proxy.js
index 2b592acb5631f84a196c887c13c8f205cfcb8abe..6e7da7164a9ea341624fbf38fbf922d7a3388d47 100644
--- a/chrome/browser/resources/settings/about_page/about_page_browser_proxy.js
+++ b/chrome/browser/resources/settings/about_page/about_page_browser_proxy.js
@@ -58,6 +58,7 @@ var UpdateStatus = {
   FAILED: 'failed',
   DISABLED: 'disabled',
   DISABLED_BY_ADMIN: 'disabled_by_admin',
+  NEED_PERMISSION_TO_UPDATE: 'need_permission_to_update',
 };
 
 // <if expr="_google_chrome and is_macosx">
@@ -213,6 +214,10 @@ cr.define('settings', function() {
       chrome.send('requestUpdate');
     },
 
+    requestUpdateOverCellular: function(target_version, target_size) {
+      chrome.send('requestUpdateOverCellular', [target_version, target_size]);
+    },

[stevenjb, 2017/05/10 23:29:05]

This should also be defined (and documented) in the prototype and marked /**
@override */ here. I'm confused why we would need to pass |target_size| here.

[weidongg, 2017/05/11 16:34:05]

I discussed with @adlr, he says
"Technically version should be enough, but there are a few scenarios where it
could try to get a delta (small) update and then fail a few times and then go
for a full update (big), which would use more data than the user agreed to.
Also, it's unlikely, but a server change could remove the delta update and leave
the full one which would be the same issue."

[stevenjb, 2017/05/11 17:20:15]

I'm still confused. It looks like we are just passing the 'size' parameter from
the 'updateStatusChaged' event back to requestUdpateOverCellular? Do we
anticipate the UI ever changing either the size or version information? It seems
like this doesn't actually need any parameters and the model (the C++ code)
should just retrieve those values?

+
     /** @override */
     setChannel: function(channel, isPowerwashAllowed) {
       chrome.send('setChannel', [channel, isPowerwashAllowed]);