Remove prefix from URL bar of PDF files

[luixxiul]

Describe the issue you encountered:
Remove the prefix chrome-extension://jkpcbbnkhhgoelcjhhgknpjcopjeande/ from the URL of a tab which opens a PDF file with the html5 reader. It must be annoying for users when they want to copy the URL.

• Platform (Win7, 8, 10? macOS? Linux distro?): OS X
• Brave Version: master branch
• STR: Open http://www.orimi.com/pdf-test.pdf
• Screenshot if needed:
  
• Any related issues: Manual test for for macOS 0.11.1 Beta1 #2513 Fix extension ID for PDFJS #2527 Preference to disable HTML5 PDF reader does not seem to work #2530