Fix context virtualization for timer queries 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/325811 Reviewed-by: Jamie Madill <jmadill@chromium.org> Commit-Queue: Ian Ewell <ewell@google.com>