Here is the list of system headers used in Glass, on Mac OS X:

#import <AppKit/NSPasteboard.h>
#import <ApplicationServices/ApplicationServices.h>
#import <Cocoa/Cocoa.h>
#import <CoreServices/CoreServices.h>
#import <Foundation/Foundation.h>
#import <JavaRuntimeSupport/JavaRuntimeSupport.h>
#import <OpenGL/OpenGL.h>
#import <OpenGL/gl.h>
#import <OpenGL/glu.h>
#import <QuartzCore/QuartzCore.h>
#import <assert.h>
#import <float.h>
#import <jni.h>
#import <mach-o/dyld.h>
#import <mach/mach.h>
#import <objc/runtime.h>
#import <pthread.h>
#import <stdio.h>
#import <sys/time.h>

Some of them are redundant and should be removed.