Make some binaries optional for sizes.py on Win
Make some binaries optional for sizes.py on Win

Since we want to use this script for WebRTC, we need to
make it work when not all the binaries the full build is creating
exists in the output.
Examples: http://build.chromium.org/p/chromium.webrtc.fyi/waterfall

BUG=none
TEST=none

Review URL: https://codereview.chromium.org/57283003

git-svn-id: 239fca9b83025a0b6f823aeeca02ba5be3d9fd76@232691 0039d316-1c4b-4281-b951-d872f2087c98

eunchong/build,eunchong/build,eunchong/build,eunchong/build