remove a dependency of surfaceflinger on libskia

libskia was only used for a small part of SkTransform. We now implement
Transform is surfaceflinger directly.
diff --git a/libs/surfaceflinger/LayerBase.h b/libs/surfaceflinger/LayerBase.h
index d1bbd04..6aacd82 100644
--- a/libs/surfaceflinger/LayerBase.h
+++ b/libs/surfaceflinger/LayerBase.h
@@ -22,6 +22,7 @@
 
 #include <EGL/egl.h>
 #include <EGL/eglext.h>
+#include <GLES/gl.h>
 
 #include <utils/RefBase.h>