Mojo: Use the unhandled exception handler for connection errors

This change also lets the unhandled exception handler take a first
attempt at handling errors that occur when handling connection errors.
yo dawg!

Bug: 810087
Test: Intentionally threw an exception from a connection error handler
Change-Id: I432055b33443208a352d272c7f7fcb1dbeb2a43f
Reviewed-on: https://chromium-review.googlesource.com/1147516Reviewed-by: Ken Rockot <rockot@chromium.org>
Commit-Queue: Luis Hector Chavez <lhchavez@chromium.org>
Cr-Commit-Position: refs/heads/master@{#577562}

mojo/public/java/bindings/src/org/chromium/mojo/bindings/Connector.java

@@ -158,7 +158,11 @@ public class Connector implements MessageReceiver, HandleOwner<MessagePipeHandle
     private void onError(MojoException exception) {
         close();
         if (mErrorHandler != null) {
-            mErrorHandler.onConnectionError(exception);
+            try {
+                mErrorHandler.onConnectionError(exception);
+            } catch (RuntimeException e) {
+                ExceptionHandler.DefaultExceptionHandler.getInstance().handleException(e);
+            }
         }
     }