[fsp] Create a RequestManager per a ProvidedFileSystem instance.
Before, there was only one single request manager per profile, and all of the
file systems were sharing it. However, it is better to create it per file
system for several reasons.
First of all, there is no need to share it, since it is lightweight, and no
data is shared between different file systems.
Secondly, it is a part of implementation of the ProvidedFileSystem. The testing
FakeProvidedFileSystem does not use a request manager at all, so there is no
need to create it for unit tests.
Also, it greatly simplifies the request manager, since there is no need to
verify the extension id and file system id every time the request manager is
used.
TEST=unit_tests: *FileSystemProvider*
BUG=248427
Review URL: https://codereview.chromium.org/239993002
git-svn-id: svn://svn.chromium.org/chrome/trunk/src@264191 0039d316-1c4b-4281-b951-d872f2087c98
12 files changed
