Old header design is still displayed for Notes and Side View Firefox experiments on 3rd party browsers

[SoftVision-PaulOiegas]

[Notes]:

• I assume this is something we have missed, including the "Firefox download" button in the new control center. Seems the only obvious reason why we still display the old UI for experiments that are Firefox experiments.

[Affected versions]:

• Chrome 67.0
• Opera 54.0
• Safari 11.1

[Affected Platforms]:

• All Windows
• All MacOS
• All Linux

[Steps to reproduce]:

1. Open 3rd party browser (Chrome, Opera, Safari) and navigate to `https://testpilot.dev.mozaws.net page.
2. Scroll down on the page to reach the available experiments.
3. Open all the available experiments in separate tabs.
4. Compere the "Color" and "Send" with "Notes" and "Side View" experiment pages when it comes to top page design.

[Expected result]:

• All 4 experiment pages have the new design implemented with only a slim blue header with logo, platform name and "Blog" button.

[Actual result]:

• Only "Color" and "Send" have the new design, while "Notes" and "Side View" still display the old header with TxP logo, Firefox download button

[Notes]:

• Here is a screenshot of the issue:

[SoftVision-PaulOiegas]

This also occurs for unsupported versions of Firefox (57, 56 and lower). Just the button differs and informs the user he needs to update.

[KhushilMistry]

Hey, I want to work on this issue. Should I remove that old header from all the experiement pages and as well from the codebase (Component of Old Header)?

[SoftVision-PaulOiegas]

I think it needs some UX from @johngruen for reminding the users that they need Firefox if they want to test the experiment. Or is it enough to have this messages on the Homepage and we don't care about the experiment details page?