Refactoring: Unify command mocks in v8 roll tests.

Refactoring: Unify command mocks in v8 roll tests.

This unifies all mocks for shell commands (like git, svn,
gclient). The command name is now explicitly stated in the
test expectations, which allows to correctly test the few
commands that are not git.

TEST=./script_test.py
TBR=jarin@chromium.org

Committed: https://code.google.com/p/v8/source/detail?r=23611

[Michael Achenbach, 2014-09-02 12:27:44]

machenbach@chromium.org changed reviewers:
+ jarin@chromium.org

[Michael Achenbach, 2014-09-02 12:28:44]

PTAL

[Michael Achenbach, 2014-09-02 12:51:39]

Committed patchset #1 (id:1) manually as 23611 (presubmit successful).

[Jarin, 2014-09-02 12:54:42]

lgtm