Image fetcher for DOM Distiller

Class to fetch an image an insert it in the DOM Distiller's
distilled page proto.

BUG=288015

Review URL: https://codereview.chromium.org/24242012

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@227779 0039d316-1c4b-4281-b951-d872f2087c98
Adding encode/decode test: Tests pipeline and bitstream compatibility between encoder and decoder. In addition, adds utility functionality for video testing, such as psnr.

Review URL: https://codereview.chromium.org/24303010

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@227780 0039d316-1c4b-4281-b951-d872f2087c98
SVN changes up to revision 227780
Bug fixes and nit cleanup, bugs found while writing a new end 2 end test.

BUG=

Review URL: https://codereview.chromium.org/25048005

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@227781 0039d316-1c4b-4281-b951-d872f2087c98
SVN changes up to revision 227781