set new math ENV.FEATURES flag based on root account, not site_admin

closes LS-1939
flag=none

we moved the flag, but didn't update the checks.

test plan:
  - enable new_math_equation_handling in site admin
  - disable in your root account
  - load any page but quiz edit or question banks in canvas
  > expect ENV.FEATURES.new_math_equation_handling to be false
  - enable the feature in your root account and load a page
  > expect ENV.FEATURES.new_math_equation_handling to be true

  - create a quiz,
  - include a comment with a math equation from the eq editor
    on one of the question answer's comments
  - on the quiz' edit page, check "show question details"
  > expect the equation in the answer's comment to be the
    equation and not MathJax output

Change-Id: If85bc04733d9bbc4e3ee1676350f5411422198fc
Reviewed-on: https://gerrit.instructure.com/c/canvas-lms/+/259562
Reviewed-by: Jeff Largent <jeff.largent@instructure.com>
QA-Review: Jeff Largent <jeff.largent@instructure.com>
Tested-by: Service Cloud Jenkins <svc.cloudjenkins@instructure.com>
Product-Review: Ed Schiebel <eschiebel@instructure.com>

app/controllers/application_controller.rb

@@ -528,6 +528,16 @@ class ApplicationController < ActionController::Base
     prepend_view_path(path)
   end
 
+  # the way classic quizzes copies question data from the page into the
+  # edit form causes the elements added for a11y to get duplicated
+  # and other misadventures that caused 4 hotfixes in 3 days.
+  # Let's just not use the new math handling there.
+  def use_new_math_equation_handling?
+    @domain_root_account&.feature_enabled?(:new_math_equation_handling) &&
+    !(params[:controller] == "quizzes/quizzes" && params[:action] == "edit") &&
+    params[:controller] != "question_banks"
+  end
+  
   protected
 
   # we track the cost of each request in RequestThrottle in order
@@ -2219,16 +2229,6 @@ class ApplicationController < ActionController::Base
     true
   end
 
-  # the way classic quizzes copies question data from the page into the
-  # edit form causes the elements added for a11y to get duplicated
-  # and other misadventures that caused 4 hotfixes in 3 days.
-  # Let's just not use the new math handling there.
-  def use_new_math_equation_handling?
-    Account.site_admin.feature_enabled?(:new_math_equation_handling) &&
-    !(params[:controller] == "quizzes/quizzes" && params[:action] == "edit") &&
-    params[:controller] != "question_banks"
-  end
-
   def destroy_session
     logger.info "Destroying session: #{session[:session_id]}"
     @pseudonym_session.destroy rescue true

app/helpers/quizzes_helper.rb

@@ -411,8 +411,7 @@ module QuizzesHelper
     html = hash_get(hash, "#{field}_html".to_sym)
 
     if html
-      use_new_math = Account.site_admin.feature_enabled?(:new_math_equation_handling) && action_name != "edit"
-      UserContent.escape(Sanitize.clean(html, CanvasSanitize::SANITIZE), nil, use_new_math)
+      UserContent.escape(Sanitize.clean(html, CanvasSanitize::SANITIZE), nil, controller.try(:use_new_math_equation_handling?))
     else
       hash_get(hash, field)
     end

spec/controllers/application_controller_spec.rb

@@ -1930,6 +1930,36 @@ describe ApplicationController do
       end
     end
   end
+
+  describe "new math equation handling feature" do
+    let(:root_account) {Account.default}
+    
+    before(:each) do
+      controller.instance_variable_set(:@domain_root_account, root_account)
+    end
+
+    it "should put false in ENV when disabled at site_admin" do
+      Account.site_admin.disable_feature!(:new_math_equation_handling)
+      expect(@controller.use_new_math_equation_handling?).to be_falsey
+      expect(@controller.js_env[:FEATURES][:new_math_equation_handling]).to be_falsey
+    end
+
+    it "should put false in ENV when enabled at site_admin but disabled at the root account" do
+      Account.site_admin.enable_feature!(:new_math_equation_handling)
+      root_account.disable_feature!(:new_math_equation_handling)
+      expect(@controller.use_new_math_equation_handling?).to be_falsey
+      expect(@controller.js_env[:FEATURES][:new_math_equation_handling]).to be_falsey
+    end
+
+    it "should put true in ENV when enabled at site_admin and the root account" do
+      Account.site_admin.enable_feature!(:new_math_equation_handling)
+      root_account.enable_feature!(:new_math_equation_handling)
+      expect(@controller.use_new_math_equation_handling?).to be_truthy
+      expect(@controller.js_env[:FEATURES][:new_math_equation_handling]).to be_truthy
+    end
+
+    
+  end
 end
 
 describe WikiPagesController do

spec/helpers/quizzes_helper_spec.rb

@@ -548,5 +548,15 @@ describe QuizzesHelper do
       expect(comment).to match(/MathML/)
       expect(comment).to match(/∐/)
     end
+
+    it 'does not add MathML if new math handling feature is active' do
+      def controller.use_new_math_equation_handling?
+        true
+      end
+      comment = comment_get({
+        foo_html: '<img class="equation_image" data-equation-content="\coprod"></img>'
+      }, 'foo')
+      expect(comment).to eq('<img class="equation_image" data-equation-content="\\coprod">')
+    end
   end
 end