Don't enable key commands flag when the command line is not set.
Don't enable key commands flag when the command line is not set.

In Safe Mode for example, the command line is unset. In such a case, don't
report the keyboard commands experiment as enabled.

BUG=564594
R=noyau@chromium.org
TEST=See bug steps.

Review URL: https://codereview.chromium.org/1501533003

Cr-Commit-Position: 972c6d2dc6dd5efdad1377c0d224e03eb8f276f7@{#363225}

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