Fix stupid bug in GLThreadManager implementation.

The code intended to copy the old value of a field, before the
field was updated. However, what the code was actually doing was
copying the new value of the field, after the field was updated.

The fix was to move the copy to before the update.

This is work towards fixing bug 2228262
diff --git a/opengl/java/android/opengl/GLSurfaceView.java b/opengl/java/android/opengl/GLSurfaceView.java
index 952eff2..ac27a2d 100644
--- a/opengl/java/android/opengl/GLSurfaceView.java
+++ b/opengl/java/android/opengl/GLSurfaceView.java
@@ -1281,8 +1281,8 @@
         public void start(GLThread thread) throws InterruptedException {
             GLThread oldThread = null;
             synchronized(this) {
-                mMostRecentGLThread = thread;
                 oldThread = mMostRecentGLThread;
+                mMostRecentGLThread = thread;
             }
             if (oldThread != null) {
                 synchronized(oldThread) {