Move FileEnumerator to its own file, do some refactoring.

It creates a class FileInfo to contain the details rather than using a platform-specific typedef. This allows the accessors GetName, GetSize, etc. to be moved directly to this class (previously they were static helpers on the FileEnumerator class) which makes a bunch of code much cleaner. It also gives reasonable getting and initialization which the previous version lacked.

BUG=175002

Reland of 198820 and 298824
Original review = https://codereview.chromium.org/13165005
R=rvargas@chromium.org

Review URL: https://codereview.chromium.org/16392011

Cr-Mirrored-From: https://chromium.googlesource.com/chromium/src
Cr-Mirrored-Commit: 25a4c1ccaee2b032ee368d733b79ac814efd7c37
2 files changed