bluetooth: android: Rename FakeBluetoothLeScanner.mCallback to mScanCallback.

This file now contains multiple callback members due to addition of mGattCallback. Instead of having them all 'mCallback' more unique names are used, and this patch updates the initial 'mCallback' to use the same style.

BUG=490430

Review URL: https://codereview.chromium.org/1357813002

Cr-Commit-Position: refs/heads/master@{#350372}
1 file changed