1172031 - Add tooltip for elided header values

Status: NEW

(DevTools :: Netmonitor, defect, P3)

Description

[Jeff Griffiths (:canuckistani) (:⚡︎)]

See https://ffdevtools.uservoice.com/forums/246087-firefox-developer-tools-ideas/suggestions/8236158-expand-truncated-ellipsis-ized-header-values-to

STR:

1. open the netmonitor
2. got to any bug, eg bug 867838
3. click on the top request, then look at the side panel and the response headers. 

If the side panel is narrow enough in width, the value of the Strict-Transport-Security header should be elided. There are two ways to access the full value but both include extra steps:

 - view the raw headers
 - click into the value, select and copy it, then paste it into a text field so that the full value is visible

The suggestion is we provide a tooltip for header values so that developers can easily see the full value by hovering over it.