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This adds a test to check that clicking the columns headers in Files
resorts the columns in the correct order. It checks for ascending and
descending.

TEST=browser_tests -gtest_filter="*SortColumns/FileManagerBrowserTest*"
BUG=None

Review URL: https://codereview.chromium.org/1063453003

Cr-Commit-Position: refs/heads/master@{#324168}