rather than symlink the webm/vpx terms, use the same header as libvpx to
reference in-tree files
based on the discussion in:
https://codereview.chromium.org/12771026/
Change-Id: Ia3067ecddefaa7ee01550136e00f7b3f086d4af4
Removed a call to WebPParseHeaders() inside VP8GetHeaders(). This was not needed
anyway, as all call flows already call WebPParseHeaders() before calling
VP8GetHeaders().
This avoids duplicate calls to WebPParseHeaders().
Change-Id: Icb2d618bd26c44220d956c17a69c9c45a62d5237