drive: Wire |has_more| callback parameters to FileSystem

fileapi::AsyncFileUtil::ReadDirectoryCallback has a boolean parameter |has_more| to return the result progressively.
Wire this parameter to FileSystem to use it later.

Add |has_more| parameter to drive::ReadDirectoryCallback.
Remove ResourceMetadata::ReadDirectoryOnUIThread.
Add a new typedef DebugInfoCollector::ReadDirectoryCallback to keep the signature unchanged.

BUG=340931
TEST=unit_tests

Review URL: https://codereview.chromium.org/141323003

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@249700 0039d316-1c4b-4281-b951-d872f2087c98
SVN changes up to revision 249700