converts content_imports/files js_block to js_bundle

test plan:
* regression test content import files

Change-Id: Ia7348b8c73d1d7528da1df546a91223d0916a2a0
Reviewed-on: https://gerrit.instructure.com/29166
Tested-by: Jenkins <jenkins@instructure.com>
Reviewed-by: Jon Jensen <jon@instructure.com>
QA-Review: Matt Fairbourn <mfairbourn@instructure.com>
Product-Review: Landon Wilkins <lwilkins@instructure.com>

app/coffeescripts/bundles/legacy/content_imports_files.coffee

@@ -0,0 +1,7 @@
+require [
+  "jquery"
+  "i18n!content_imports.files"
+], ($, I18n) ->
+  $ ->
+    $("#zip_file_import_form .cancel_button").attr("href", ENV.return_or_context_url).text (if ENV.return_to then I18n.t("buttons.cancel", "Cancel") else I18n.t("buttons.skip", "Skip this Step"))
+

app/controllers/content_imports_controller.rb

@@ -23,6 +23,7 @@ class ContentImportsController < ApplicationController
   prepend_around_filter :load_pseudonym_from_policy, :only => :migrate_content_upload
   
   include Api::V1::Course
+  include ContentImportsHelper
 
   COPY_TYPES = %w{assignment_groups assignments context_modules learning_outcomes
                 quizzes assessment_question_banks folders attachments wiki_pages discussion_topics
@@ -39,6 +40,8 @@ class ContentImportsController < ApplicationController
   # current files UI uses this page for .zip uploads
   def files
     authorized_action(@context, @current_user, [:manage_content, :manage_files])
+    js_env(return_or_context_url: return_or_context_url,
+           return_to: params[:return_to])
   end
 
   # @API Get course copy status

app/views/content_imports/files.html.erb

@@ -6,17 +6,4 @@
   </p>
   <%= render :partial => 'shared/zip_file_import_form' %>
 </div>
-<% js_block do %>
-<script type="text/javascript">
-require([
-  'jquery' /* $ */
-], function($) {
-
-  $(function(){
-    $("#zip_file_import_form .cancel_button")
-      .attr("href", "<%= return_or_context_url %>")
-      .text(<%= params[:return_to] ? t('#buttons.cancel', "Cancel").to_json.html_safe : t('buttons.skip', "Skip this Step").to_json.html_safe %>);
-  });
-});
-</script>
-<% end %>
+<% js_bundle 'legacy/content_imports_files' %>