Fix the coordinates for touch selection.

* The selection bounds attached to CompositorFrameMetaData is in viewport coordinates.  This needs to be converted to DIP for browser somewhere. For now, this CL convert it in browser  side rather than renderer side because the code that computes the selection bounds is in cc/  rather than content/renderer. Consider move that part ot content/renderer and move this to there instead.

BUG=585043
TEST=TouchSelectionControllerClientAuraScaleFactorTest*. manual.

Review URL: https://codereview.chromium.org/1740193002

Cr-Commit-Position: refs/heads/master@{#378500}
5 files changed