In the current implementation of query virtualization, queries are
paused/resumed during draw calls. Timer queries however are affected by
every OpenGL call, so virtualization and context switches for timer
queries must happen every time there is a context switch. Thus the logic
for context-switching queries was moved to a new function in the GL state
manager that is called everytime a makeCurrent call on the context is
made. Since queries may be made after a context is made current, the state
manager needs to keep track of any new queries that are started in a
context, so an additional delegate function was added to the state manager
that is called every time a glBeginQuery() call is made that adds the
query object to a set. All the queries in that set are paused when a
context switch is made and the queries in the new context are then loaded
and resumed.

BUG=angleproject:1307

Change-Id: I4e596d83739274cb2e14152a39e86e0e51b0f95c
Reviewed-on: https://chromium-review.googlesource.com/325811Reviewed-by: Jamie Madill <jmadill@chromium.org>
Commit-Queue: Ian Ewell <ewell@google.com>