[fsp] Introduce file_system_provider::Service class for the FileSystemProvider API.
This patch introduces a service which manages file systems provided by third party extensions.
The class has two methods: registerFileSystem() and unregisterFileSystem() which are supposed to be called from
chrome.fileSystemProvider.* api methods. The service stores a map of the registered file systems, mounts them, and
notifies observers (VolumeManager) about the fact.
The file system backend does not handle the new file system type yet, this will be done separately.
TEST=browser_test, unit_tests: *FileSystemProvider*
BUG=248427
Review URL: https://codereview.chromium.org/192573002
git-svn-id: svn://svn.chromium.org/chrome/trunk/src@259820 0039d316-1c4b-4281-b951-d872f2087c98
25 files changed
