ThreadLocalStorage: Add a function to destroy pthread key used in libchrome

MojoProcessSupport needs to destroy pthread key which is globally used in libchrome. The key is
stored in a local variable in thread_local_storage.cc.
This adds a function to destroy the key so that MojoProcessSupport can do it.

Bug: 110722333
Test: No crash in opening DRMInfo.app
Test: PlayStore still works
Test: cheets_ContainerSmokeTest and cheets_LoginScreen
Change-Id: Ib10c83deb5f7ef141d4ab9883e0d2c31d422a1b1
3 files changed