Android: Add helper function to synchronously execute Callables on Handler

talk/app/webrtc/java/android/org/webrtc/ThreadUtils.java

Index: talk/app/webrtc/java/android/org/webrtc/ThreadUtils.java
diff --git a/talk/app/webrtc/java/android/org/webrtc/ThreadUtils.java b/talk/app/webrtc/java/android/org/webrtc/ThreadUtils.java
index 5e6cc52895c8ce44fb63201f632c3cb269044777..33402f700ba014c6393c1ea708bd1e3a5616bc30 100644
--- a/talk/app/webrtc/java/android/org/webrtc/ThreadUtils.java
+++ b/talk/app/webrtc/java/android/org/webrtc/ThreadUtils.java
@@ -27,6 +27,9 @@
 
 package org.webrtc;
 
+import android.os.Handler;
+
+import java.util.concurrent.Callable;
 import java.util.concurrent.CountDownLatch;
 
 final class ThreadUtils {
@@ -100,4 +103,27 @@ final class ThreadUtils {
       }
     });
   }
+
+  /**
+   * Post |callable| to |handler| and wait for the result.
+   */
+  public static <V> V invokeUninterruptibly(final Handler handler, final Callable<V> callable) {
+    class Result {
+      public V value;
+    }
+    final Result result = new Result();
+    final CountDownLatch barrier = new CountDownLatch(1);
+    handler.post(new Runnable() {
+      @Override public void run() {
+        try {
+          result.value = callable.call();
+        } catch (Exception e) {
+          throw new RuntimeException("Callable threw exception: " + e);

[hbos, 2015/10/12 08:20:19]

On second thought, this will catch InterruptedExceptions too and wrap them in
RuntimeExceptions, meaning it will not get caught and it will crash.

You need to catch InterruptedException and rethrow it without wrapping
separately. Fix in a follow-up CL.

[magjed_webrtc, 2015/10/12 14:29:01]

Actually, this is correct. The InterruptedException has nothing to do with the
callable. InterruptedException may be thrown by barrier.await() and that is
handled in 'awaitUninterruptibly(barrier)'.

+        }
+        barrier.countDown();
+      }
+    });
+    awaitUninterruptibly(barrier);
+    return result.value;
+  }
 }