GLES2Debugger: Make command exchange async to improve performance.

In message loop, use select to check for available commands from client,
 rather than always expecting commands in eglSwapBuffers.
Client can send commands at any time.

Change-Id: I607c8fa571a896996c0a3300de904b6e263fc281
Signed-off-by: David Li <davidxli@google.com>
4 files changed