GitLab

Rename SyntheticPointer to SyntheticPointerDriver, SyntheticTouchPointer to
SyntheticTouchDriver, and SyntheticMousePointer to SyntheticMouseDriver,
because these classes do not represent the synthetic pointers. They actually create
synthetic pointers for each pointer types and their actions.

BUG=525187

Review-Url: https://codereview.chromium.org/2478423002
Cr-Commit-Position: refs/heads/master@{#434763}