A feature flag to toggle html5/flash first video playback

this is a simple feature flag that will let us
toggle between:
a. trying html5 first then falling back to flash
   if not enabled or trying flash first.
b. trying flash first, then falling back to html5
   if unavailable.

test plan:
1. with feature flag not turned on, watch a video.
it should use flash to play it.
2. turn on the feature flag for domain_root_account
3. watch a video, it should use html5

Change-Id: I08aab043f89d049863dcbbd49aa1c4fcd8dc2895
Reviewed-on: https://gerrit.instructure.com/34248
Tested-by: Jenkins <jenkins@instructure.com>
Reviewed-by: David Julia <djulia@pivotallabs.com>
Reviewed-by: Paul Hinze <paulh@instructure.com>
Product-Review: Ben Hutchings <benh@instructure.com>
QA-Review: Steven Shepherd <sshepherd@instructure.com>

app/coffeescripts/jquery/mediaComment.coffee

@@ -20,6 +20,11 @@ define [
     # default if the <video height> is not specified
     defaultVideoHeight: VIDEO_HEIGHT
 
+  unless INST.enableHtml5FirstVideos
+    # prefer flash player, as it works more consistently
+    # for now, but allow fallback to html5 (like on mobile)
+    mejs.MepDefaults.mode = 'auto_plugin'
+
   mejs.MepDefaults.success = (mediaElement, domObject) ->
     kalturaAnalytics(this.mediaCommentId, mediaElement, INST.kalturaSettings)
     mediaElement.play()

app/helpers/application_helper.rb

@@ -484,6 +484,7 @@ module ApplicationHelper
       :disableScribdPreviews    => !feature_enabled?(:scribd),
       :disableCrocodocPreviews  => !feature_enabled?(:crocodoc),
       :enableScribdHtml5        => feature_enabled?(:scribd_html5),
+      :enableHtml5FirstVideos   => @domain_root_account.feature_enabled?(:html5_first_videos),
       :logPageViews             => !@body_class_no_headers,
       :maxVisibleEditorButtons  => 3,
       :editorButtons            => editor_buttons,

lib/feature.rb

@@ -109,6 +109,18 @@ END
       description: -> { I18n.t('new_styles_description', <<-END) },
 We are working on a UI facelift to Canvas. Turn this on to opt-in to seeing the
 updated, simplified look and feel of the Canvas interface.
+END
+      applies_to: 'RootAccount',
+      state: 'allowed',
+      beta: true,
+      development: true
+    },
+    'html5_first_videos' =>
+    {
+      display_name: -> { I18n.t('features.html5_first_videos', 'Prefer HTML5 for video playback') },
+      description: -> { I18n.t('html5_first_videos_description', <<-END) },
+By default, Canvas will try to use Flash first to play videos. Turn this on to try using HTML5 first,
+then fall back to Flash.
 END
       applies_to: 'RootAccount',
       state: 'allowed',