Clean up LappedTransform and Blocker.

  - Remove unnecessary window member from lapped_transform.
  - Add comment indicated that Blocker does not take ownership of
    the window passed to its constructor.
  - Streamline LappedTransform constructor so members can be const.

Also use a range-based for loop in audio_processing_impl.cc for clarity.

R=aluebs@webrtc.org, andrew@webrtc.org

Review URL: https://webrtc-codereview.appspot.com/41229004

Cr-Original-Commit-Position: refs/heads/master@{#8708}
Cr-Mirrored-From: https://chromium.googlesource.com/external/webrtc
Cr-Mirrored-Commit: e534086492e92c45d74b176f3c8be4addb69713f
7 files changed