[sync] Allow FakeURLFetcher to return arbitrary HTTP response codes

As of today, FakeURLFetcher takes a boolean "success" parameter, and
returns one of two HTTP response codes: 200 for success and 500 for
failure.

In order to write sync tests for auth errors, we need to be able to fake
arbitrary HTTP response codes.

This patch modifies FakeURLFetcher to return arbitrary HTTP response
codes and fixes all existing call sites. Tests that return arbitrary
error codes will be added in a separate CL.

R=achuith@chromium.org, ajwong@chromium.org, akalin@chromium.org, bengr@chromium.org, nyquist@chromium.org, sergeyu@chromium.org, vitalybuka@chromium.org
TBR=battre, mattm, sky, stevenjb, tim
BUG=313905
TEST=All existing tests pass trybots and waterfall

Review URL: https://codereview.chromium.org/48713008

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@232724 0039d316-1c4b-4281-b951-d872f2087c98
SVN changes up to revision 232724
Disable AcceleratorControllerTest.SuppressToggleMaximized

TBR=mtomasz@chromium.org
BUG=314674

Review URL: https://codereview.chromium.org/58013002

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@232725 0039d316-1c4b-4281-b951-d872f2087c98
SVN changes up to revision 232725