correct body word count with <br>

closes EVAL-4019
flag=none

Test Plan:
- Create a text entry assignment
- As a student, start your submission
- Add a single word to the submission box, hit shift+return/enter to add
 a line break, then add a second word
- Notice that the the total word count below the RCE shows 2 words
- Submit to the assignment
- Navigate to Speedgrader and view the word count. Notice that it shows
that there is 2 words and matches the RCE count.

Change-Id: I6ad8b20eff50805a12ffef0362adaaa5bbe96050
Reviewed-on: https://gerrit.instructure.com/c/canvas-lms/+/345625
Tested-by: Service Cloud Jenkins <svc.cloudjenkins@instructure.com>
Reviewed-by: Aaron Shafovaloff <ashafovaloff@instructure.com>
QA-Review: Cameron Ray <cameron.ray@instructure.com>
Product-Review: Cameron Ray <cameron.ray@instructure.com>

app/models/submission.rb

@@ -3043,8 +3043,15 @@ def grading_status
 
   def word_count
     if body && submission_type != "online_quiz"
-      tinymce_wordcount_count_regex = /[\w\u2019\x27\-\u00C0-\u1FFF]+/
-      ActionController::Base.helpers.strip_tags(body).scan(tinymce_wordcount_count_regex).size
+      segments = body.split(%r{<br\s*/?>})
+      word_count = 0
+      segments.each do |segment|
+        tinymce_wordcount_count_regex = /(?:[\w\u2019\x27\-\u00C0-\u1FFF]+|(?<=<br>)([^<]+)|([^<]+)(?=<br>))/
+        words = ActionController::Base.helpers.strip_tags(segment).scan(tinymce_wordcount_count_regex).size
+        word_count += words
+      end
+
+      word_count
     elsif versioned_attachments.present?
       Attachment.where(id: versioned_attachments.pluck(:id)).sum(:word_count)
     end

spec/models/submission_spec.rb

@@ -8973,6 +8973,11 @@ def check_cache_clear
       expect(submission.word_count).to eq 2
     end
 
+    it "returns the word count if body is split up by <br> tags" do
+      submission.update(body: "test<br>submission")
+      expect(submission.word_count).to eq 2
+    end
+
     it "returns nil if there is no body" do
       expect(submission.body).to be_nil
       expect(submission.word_count).to be_nil