Enable all tests in CopylessPasteTest

The following tests are re-enabled:
- testValid
- testNoMeta
- testCache

All flaky failures in CopylessPasteTest are due to timeout in
CallbackHelper.waitForCallback(). Wait for longer to see if it gets
better.

Reference:
https://test-results.appspot.com/dashboards/flakiness_dashboard.html#testType=chrome_public_test_apk%20(with%20patch)&showAllRuns=true&tests=org.chromium.chrome.browser.CopylessPasteTest%23

BUG=713172,713895,713878,693650

Review-Url: https://codereview.chromium.org/2826253004
Cr-Commit-Position: refs/heads/master@{#485865}
1 file changed