FileAPI: Add WebFileSystem::resolveURL

This introduces WebFileSystem::resolveURL so that resolveLocalFileSystemURL,
a member of FileSystem API, can resolve a filesystem URL for external
filesystem.

This includes:
- Cracking the given filesystem URL not in Blink side but in Chromium side so
that we can get more specific external filesystem type (e.g. SyncFileSystem).
It is necessary to resolve the external filesystem URL.
- Replacing readFileSystem with resolveURL since it's used only to resolve URLs.
- Changing the error code, and these must be correct:
(http://dev.w3.org/2009/dap/file-system/file-dir-sys.html#errors-and-exceptions)

Depends on Chromium side change:
https://codereview.chromium.org/23856002/


BUG=177137
TEST=run_webkit_tests.sh http/tests/filesystem/\*
TEST=run_webkit_tests.sh http/tests/inspector/filesystem/\*

Review URL: https://chromiumcodereview.appspot.com/23537011

git-svn-id: svn://svn.chromium.org/blink/trunk@158157 bbb929c8-8fbe-4397-9dbb-9b2b20218538