Revert of Add GN build rules to allow java_assertion_enabler to enable Java asserts.

media/midi/java/src/org/chromium/midi/MidiManagerAndroid.java

Index: media/midi/java/src/org/chromium/midi/MidiManagerAndroid.java
diff --git a/media/midi/java/src/org/chromium/midi/MidiManagerAndroid.java b/media/midi/java/src/org/chromium/midi/MidiManagerAndroid.java
index 6f817c5f042853cafe49633866609367a3c783a0..410fbbd0039fe75f735950086dff923187e47a27 100644
--- a/media/midi/java/src/org/chromium/midi/MidiManagerAndroid.java
+++ b/media/midi/java/src/org/chromium/midi/MidiManagerAndroid.java
@@ -67,8 +67,7 @@
      * @param nativeManagerPointer The native pointer to a midi::MidiManagerAndroid object.
      */
     private MidiManagerAndroid(Context context, long nativeManagerPointer) {
-        // TODO(crbug.com/665157)
-        // assert ThreadUtils.runningOnUiThread();
+        assert ThreadUtils.runningOnUiThread();
 
         mManager = (MidiManager) context.getSystemService(Context.MIDI_SERVICE);
         mHandler = new Handler(ThreadUtils.getUiThreadLooper());