Revert 244229 "base: Fix registering of memory pressure listener..."

Revert 244229 "base: Fix registering of memory pressure listener..."

Causing webkit_unit_tests to fail.

> base: Fix registering of memory pressure listeners used when emulating discardable memory.
> 
> Memory pressure listeners need to be created on a thread with a message
> loop current. Discardable memory is often used on worker threads that
> don't have a message loop and with the current system where listeners
> are registered on first use, the result is that we're most likely never
> notified of memory pressure.
> 
> This adds a function to the discardable memory interface that allows us
> to register memory pressure listeners on a thread, and at a time, when
> we know a message loop is current.
> 
> BUG=332570
> TBR=jamesr@chromium.org
> 
> Review URL: https://codereview.chromium.org/129963002

TBR=reveman@chromium.org

Committed: https://src.chromium.org/viewvc/chrome?view=rev&revision=244278

[reveman, 2014-01-11 00:08:21]

Committed patchset #1 manually as r244278.