Remove deprecated NodeData class.

R=titzer@chromium.org

Review URL: https://codereview.chromium.org/768853002

Cr-Commit-Position: refs/heads/master@{#25575}
Abstract platform in perf runner.

This is basically a refactoring that extracts desktop
specific code into a separate class.

Also adds flags for android runs (not used yet).

BUG=chromium:374740
LOG=n
TEST=python -m unittest run_perf_test
NOTRY=true

Review URL: https://codereview.chromium.org/762163002

Cr-Commit-Position: refs/heads/master@{#25576}