Handle platforms with no bluetooth in AudioManagerAndroid.

AudioManagerAndroid will NPE on hardware platforms that don't
have bluetooth.

BUG=401039

Review URL: https://codereview.chromium.org/449463002

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@287813 0039d316-1c4b-4281-b951-d872f2087c98

media/base/android/java/src/org/chromium/media/AudioManagerAndroid.java

@@ -664,6 +664,11 @@ class AudioManagerAndroid {
             btAdapter = BluetoothAdapter.getDefaultAdapter();
         }
 
+        if (btAdapter == null) {
+            // Bluetooth not supported on this platform.
+            return false;
+        }
+
         int profileConnectionState;
         profileConnectionState = btAdapter.getProfileConnectionState(
                 android.bluetooth.BluetoothProfile.HEADSET);