Support Ruby 2.2

railties/test/application/asset_debugging_test.rb

@@ -13,7 +13,7 @@ def setup
 
       app_file "app/assets/javascripts/application.js", "//= require_tree ."
       app_file "app/assets/javascripts/xmlhr.js", "function f1() { alert(); }"
-      app_file "app/assets/config/manifest.js", <<~JS
+      app_file "app/assets/config/manifest.js", <<-JS.strip_heredoc
         //= link_tree ../images
         //= link_directory ../stylesheets .css
         //= link_directory ../javascripts .js

railties/test/application/assets_test.rb

@@ -545,7 +545,7 @@ def app_with_assets_in_view
         app_file "app/assets/javascripts/application.js", "//= require_tree ."
         app_file "app/assets/javascripts/xmlhr.js", "function f1() { alert(); }"
         app_file "app/views/posts/index.html.erb", "<%= javascript_include_tag 'application' %>"
-        app_file "app/assets/config/manifest.js", <<~JS
+        app_file "app/assets/config/manifest.js", <<-JS.strip_heredoc
           //= link_tree ../images
           //= link_directory ../stylesheets .css
           //= link_directory ../javascripts .js