Clean up LayoutSVGShape::NodeAtPoint

Since LayoutSVGShape::NodeAtPointInternal is now only called from
LayoutSVGShape::NodeAtPoint, we can make it private. Rename it to
something more helper-like - HitTestShape.

Move the check of 'visibility' to LayoutSVGShape::NodeAtPoint from
HitTestShape, to better match other similar methods.

Change-Id: If251b8b9258b754bfc94044739d6a8c41f1b04e7
Reviewed-on: https://chromium-review.googlesource.com/c/1352253
Reviewed-by: Philip Rogers <pdr@chromium.org>
Commit-Queue: Fredrik Söderquist <fs@opera.com>
Cr-Commit-Position: refs/heads/master@{#611618}
2 files changed