[fsp] Add support for opening files.
This patch adds support to opening a file. It is currently no-op, and it is
not yet bound to fileapi.
In order to bound it to fileapi::AsyncFileUtil, we need to implement closing
operation, and reading operations first. Otherwise, creating a snapshot
(required by fileapi::AsyncFileUtil) is not possible.
TEST=unit_tests: *FileSystemProvider*OpenFile*
BUG=248427
Review URL: https://codereview.chromium.org/284443002
git-svn-id: svn://svn.chromium.org/chrome/trunk/src@270040 0039d316-1c4b-4281-b951-d872f2087c98
15 files changed
