Copy DatabaseTask.{h,cpp} to TaskSynchronizer.{h,cpp}

Copy DatabaseTask.{h,cpp} to TaskSynchronizer.{h,cpp}

This CL just copies a file just to make the diff of
https://codereview.chromium.org/198673002/ saner.

TBR=tkent
NOTRY=true

Committed: https://src.chromium.org/viewvc/blink?view=rev&revision=170531

[haraken, 2014-04-01 08:07:18]

Committed patchset #1 manually as r170531.

[tkent, 2014-04-02 01:33:42]

lgtm