emulator/opengl: Add global lock to libOpenglRender.

This patch ensures that all render threads use the same global
lock to synchronize calls to the underlying GLES/EGL libraries.

Original patch from Thomas Knych (thomaswk@google.com)

BUG=9627179

Change-Id: I8ac9a43bc30bba8a9a06f832cf29e72263d946ce
4 files changed