egl: Differentiate pending vs invalid timestamps.

Test: adb shell /data/nativetest/libgui_test/libgui_test
    --gtest_filter=*GetFrameTimestamps*

Change-Id: Iaa418ff1753a4339bfefaa68a6b03e8c96366a87
diff --git a/opengl/include/EGL/eglext.h b/opengl/include/EGL/eglext.h
index bf831a7..3068029 100644
--- a/opengl/include/EGL/eglext.h
+++ b/opengl/include/EGL/eglext.h
@@ -640,6 +640,8 @@
 #define EGL_DISPLAY_PRESENT_TIME_ANDROID 0x3157
 #define EGL_DEQUEUE_READY_TIME_ANDROID 0x3158
 #define EGL_READS_DONE_TIME_ANDROID 0x3159
+#define EGL_TIMESTAMP_PENDING_ANDROID EGL_CAST(EGLnsecsANDROID, -2)
+#define EGL_TIMESTAMP_INVALID_ANDROID EGL_CAST(EGLnsecsANDROID, -1)
 #ifdef EGL_EGLEXT_PROTOTYPES
 EGLAPI EGLBoolean eglGetNextFrameIdANDROID(EGLDisplay dpy, EGLSurface surface, EGLuint64KHR *frameId);
 EGLAPI EGLBoolean eglGetCompositorTimingANDROID(EGLDisplay dpy, EGLSurface surface, EGLint numTimestamps, const EGLint *names, EGLnsecsANDROID *values);