diff --git a/opengl/tools/glgen/gen b/opengl/tools/glgen/gen
index 41fcf1b..9efd38f 100755
--- a/opengl/tools/glgen/gen
+++ b/opengl/tools/glgen/gen
@@ -1,6 +1,18 @@
 #!/bin/bash
 set -u
 set -e
+
+if [ -z "$ANDROID_BUILD_TOP" ] ; then
+    echo "ANDROID_BUILD_TOP is not set, did you run lunch?"
+    exit 1
+fi
+
+# Avoid spewing files in any location other than the intended one.
+if [ ! -x "$PWD/gen" ] ; then
+    echo "Run this script from its parent directory".
+    exit 1
+fi
+
 rm -rf out generated
 
 mkdir out
@@ -92,7 +104,7 @@
 
 # Add UnsupportedAppUsage.java to known sources.
 mkdir -p out/android/compat/annotation
-cp ../../../../../tools/platform-compat/annotation/src/java/android/compat/annotation/UnsupportedAppUsage.java out/android/compat/annotation
+cp ${ANDROID_BUILD_TOP}/tools/platform-compat/java/android/compat/annotation/UnsupportedAppUsage.java out/android/compat/annotation
 
 pushd out > /dev/null
 mkdir classes
@@ -153,23 +165,23 @@
     fi
 }
 
-compareGenerated ../../../../base/core/jni generated/C com_google_android_gles_jni_GLImpl.cpp
-compareGenerated ../../../../base/opengl/java/com/google/android/gles_jni generated/com/google/android/gles_jni GLImpl.java
+compareGenerated ${ANDROID_BUILD_TOP}/frameworks/base/core/jni generated/C com_google_android_gles_jni_GLImpl.cpp
+compareGenerated ${ANDROID_BUILD_TOP}/frameworks/base/opengl/java/com/google/android/gles_jni generated/com/google/android/gles_jni GLImpl.java
 
 for x in GL.java GL10.java GL10Ext.java GL11.java GL11Ext.java GL11ExtensionPack.java
 do
-    compareGenerated ../../../../base/opengl/java/javax/microedition/khronos/opengles generated/javax/microedition/khronos/opengles $x
+    compareGenerated ${ANDROID_BUILD_TOP}/frameworks/base/opengl/java/javax/microedition/khronos/opengles generated/javax/microedition/khronos/opengles $x
 done
 
 for x in EGL14 EGL15 EGLExt GLES10 GLES10Ext GLES11 GLES11Ext GLES20 GLES30 GLES31 GLES31Ext GLES32
 do
-    compareGenerated ../../../../base/opengl/java/android/opengl generated/android/opengl ${x}.java
-    compareGenerated ../../../../base/core/jni generated/C android_opengl_${x}.cpp
+    compareGenerated ${ANDROID_BUILD_TOP}/frameworks/base/opengl/java/android/opengl generated/android/opengl ${x}.java
+    compareGenerated ${ANDROID_BUILD_TOP}/frameworks/base/core/jni generated/C android_opengl_${x}.cpp
 done
 
 for x in EGLConfig EGLContext EGLDisplay EGLObjectHandle EGLSurface EGLImage EGLSync
 do
-    compareGenerated ../../../../base/opengl/java/android/opengl generated/android/opengl ${x}.java
+    compareGenerated ${ANDROID_BUILD_TOP}/frameworks/base/opengl/java/android/opengl generated/android/opengl ${x}.java
 done
 
 if [ $KEEP_GENERATED == "0" ] ; then
diff --git a/opengl/tools/glgen/stubs/egl/EGL14Header.java-if b/opengl/tools/glgen/stubs/egl/EGL14Header.java-if
index 9932556..951ecff 100644
--- a/opengl/tools/glgen/stubs/egl/EGL14Header.java-if
+++ b/opengl/tools/glgen/stubs/egl/EGL14Header.java-if
@@ -21,8 +21,8 @@
 import android.compat.annotation.UnsupportedAppUsage;
 import android.graphics.SurfaceTexture;
 import android.view.Surface;
-import android.view.SurfaceView;
 import android.view.SurfaceHolder;
+import android.view.SurfaceView;
 
 /**
  * EGL 1.4
diff --git a/opengl/tools/glgen/stubs/jsr239/GLImplHeader.java-impl b/opengl/tools/glgen/stubs/jsr239/GLImplHeader.java-impl
index afcc3eb..32c9d7d 100644
--- a/opengl/tools/glgen/stubs/jsr239/GLImplHeader.java-impl
+++ b/opengl/tools/glgen/stubs/jsr239/GLImplHeader.java-impl
@@ -19,6 +19,7 @@
 package com.google.android.gles_jni;
 
 import android.app.AppGlobals;
+import android.compat.annotation.UnsupportedAppUsage;
 import android.content.pm.ApplicationInfo;
 import android.content.pm.IPackageManager;
 import android.os.Build;
@@ -26,6 +27,7 @@
 import android.util.Log;
 
 import java.nio.Buffer;
+
 import javax.microedition.khronos.opengles.GL10;
 import javax.microedition.khronos.opengles.GL10Ext;
 import javax.microedition.khronos.opengles.GL11;
@@ -55,6 +57,7 @@
     private boolean have_OES_framebuffer_object;
     private boolean have_OES_texture_cube_map;
 
+    @UnsupportedAppUsage
     public GLImpl() {
     }