Kibana: Default text in profiler is not visible in dark mode

[bhavyarm]

Kibana version: 7.2.0 BC5

Elasticsearch version: 7.2.0 BC5

Server OS version: darwin_x86_64

Browser version: chrome latest

Browser OS version: os x

Original install method (e.g. download page, yum, from source, etc.): from staging

Describe the bug: Default text _all is not visible on search profiler screen.

[elasticmachine]

Pinging @elastic/es-ui

[cjcenizal]

@elastic/eui-design Could you address this in EUI?

[cchaos]

These components are still Bootstrap. It is already addressed in EUI, but this app needs to be converted.

[barlowm]

This is a Level AA Violation
Also, as mentioned in #38551 this appears to be Mac OS specific.

[cchaos]

That input is using placeholder text:

The best way to just make this compliant is making that the value of the input instead of a placeholder.