Add ffmpeg and zxing to webrtc/tools/video_quality_toolchain.

Usually .sha1 files are downlaoded using DEPS hooks but since this
bucket is internal we can't run it everywhere since it would fail
non-Googler checkouts. Instead we download the binaries by calling
a Python script, which will be added as a separate build step on the
buildbots.

The .sha1 files are copied from
https://cs.chromium.org/chromium/src/chrome/test/data/webrtc/resources/tools/
leaving out pesq and sox.

BUG=webrtc:6633
TESTED=Ran the download.py script on Mac and verified the files were downloaded.
R=mandermo@google.com, phoglund@webrtc.org

Review URL: https://codereview.webrtc.org/2462023002 .

Cr-Commit-Position: refs/heads/master@{#14859}

tools/video_quality_toolchain/download.py

@@ -0,0 +1,35 @@
+#!/usr/bin/env python
+# Copyright (c) 2016 The WebRTC project authors. All Rights Reserved.
+#
+# Use of this source code is governed by a BSD-style license
+# that can be found in the LICENSE file in the root of the source
+# tree. An additional intellectual property rights grant can be found
+# in the file PATENTS.  All contributing project authors may
+# be found in the AUTHORS file in the root of the source tree.
+
+"""Downloads precompiled tools needed for video quality analysis."""
+
+import os
+import subprocess
+import sys
+
+
+SCRIPT_DIR = os.path.dirname(os.path.abspath(__file__))
+
+
+def main():
+  cmd = [
+    'download_from_google_storage',
+    '--directory',
+    '--num_threads=10',
+    '--bucket', 'chrome-webrtc-resources',
+    '--auto_platform',
+    '--recursive',
+    SCRIPT_DIR,
+  ]
+  print 'Downloading video quality analysis tools...'
+  subprocess.check_call(cmd)
+
+
+if __name__ == '__main__':
+  sys.exit(main())