repairs CopyFromCompositingSurface in HighDPI

This CL removes the DIP=>Pixel transform in
DelegatedFrameHost::CopyFromCompositingSurface(), because said
transformation seems to be happening later in the copy logic
and is currently being applied twice.

BUG=397708

Review URL: https://codereview.chromium.org/421293002

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@286414 0039d316-1c4b-4281-b951-d872f2087c98