Fix back button does not disconnect remoting session

remoting/android/java/src/org/chromium/chromoting/Desktop.java

 // Copyright 2013 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 package org.chromium.chromoting;
 
 import android.annotation.SuppressLint;
 import android.app.Activity;
 import android.content.res.Configuration;
 import android.os.Build;
@@ skipping 165 matching lines @@
         return super.onOptionsItemSelected(item);
     }
 
     /**
      * Called once when a keyboard key is pressed, then again when that same key is released. This
      * is not guaranteed to be notified of all soft keyboard events: certian keyboards might not
      * call it at all, while others might skip it in certain situations (e.g. swipe input).
      */
     @Override
     public boolean dispatchKeyEvent(KeyEvent event) {
+        int keyCode = event.getKeyCode();
+
+        // Dispatch the back button to the system to handle navigation
+        if (keyCode == KeyEvent.KEYCODE_BACK) {
+            return super.dispatchKeyEvent(event);
+        }
+
         // Send TextEvent in two cases:
         //   1. This is an ACTION_MULTIPLE event.
         //   2. The event was generated by on-screen keyboard and Ctrl, Alt and
         //      Meta are not pressed.
         // This ensures that on-screen keyboard always injects input that
         // correspond to what user sees on the screen, while physical keyboard
         // acts as if it is connected to the remote host.
         if (event.getAction() == KeyEvent.ACTION_MULTIPLE) {
             JniInterface.sendTextEvent(event.getCharacters());
-            return super.dispatchKeyEvent(event);
+            return true;
         }
 
-        int keyCode = event.getKeyCode();
         boolean pressed = event.getAction() == KeyEvent.ACTION_DOWN;
 
         // For Enter getUnicodeChar() returns 10 (line feed), but we still
         // want to send it as KeyEvent.
         int unicode = keyCode != KeyEvent.KEYCODE_ENTER ? event.getUnicodeChar() : 0;
 
         boolean no_modifiers = !event.isAltPressed() &&
                                !event.isCtrlPressed() && !event.isMetaPressed();
 
         if (event.getDeviceId() == KeyCharacterMap.VIRTUAL_KEYBOARD &&
@@ skipping 29 matching lines @@
                 JniInterface.sendKeyEvent(KeyEvent.KEYCODE_SHIFT_LEFT, pressed);
                 JniInterface.sendKeyEvent(KeyEvent.KEYCODE_EQUALS, pressed);
                 return true;
 
             default:
                 // We try to send all other key codes to the host directly.
                 return JniInterface.sendKeyEvent(keyCode, pressed);
         }
     }
 }