synchronized back some methods. seems to fix rnc-archive#21

Author: gre

android/src/main/java/fr/greweb/rnwebgl/RNWebGLView.java

@@ -58,7 +58,7 @@ public void run() {
     }
   }
 
-  public void onDrawFrame(GL10 unused) {
+  public synchronized void onDrawFrame(GL10 unused) {
     // Flush any queued events
     for (Runnable r : mEventQueue) {
       r.run();
@@ -83,11 +83,11 @@ public void onDetachedFromWindow() {
     super.onDetachedFromWindow();
   }
 
-  public void runOnGLThread(Runnable r) {
+  public synchronized void runOnGLThread(Runnable r) {
     mEventQueue.add(r);
   }
 
-  public static void runOnGLThread(int ctxId, Runnable r) {
+  public synchronized static void runOnGLThread(int ctxId, Runnable r) {
     RNWebGLView glView = mGLViewMap.get(ctxId);
     if (glView != null) {
       glView.runOnGLThread(r);