Fixed startup test branding issue on Mac.
Fixed startup test branding issue on Mac.

The test started failing after r90141, which fixed a "Chrome" versus "Chromium"
branding issue on reference builds. Now the test should pass.

BUG=90895
TEST=performance_ui_tests --gtest_filter=StartupTest.PerfRestoreFewTabsReference


Review URL: http://codereview.chromium.org/7532008

git-svn-id: de016e52bd170d2d4f2344f9bf92d50478b649e0@94596 0039d316-1c4b-4281-b951-d872f2087c98

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