Fix #3923 - Playlist Gesture Recognizer within iFrame

[Brandon-T]

• Makes playlist video detection more robust when iFrames and gestures are involved.

Summary of Changes

This pull request fixes #3923

Submitter Checklist:

• Unit Tests are updated to cover new or changed functionality
• User-facing strings use NSLocalizableString()

Test Plan:

• Included in the ticket.

Screenshots:

Reviewer Checklist:

• Issues include necessary QA labels:
  • QA/(Yes|No)
  • bug / enhancement
• Necessary security reviews have taken place.
• Adequate unit test coverage exists to prevent regressions.
• Adequate test plan exists for QA to validate (if applicable).
• Issue and pull request is assigned to a milestone (should happen at merge time).