Fix incorrectly painted right floats in LayoutNG

This patch fixes several problems discovered while investigating the
issue with incorrectly painted right floats in LayoutNG.

List of changes:

1) NGFloatingObject.parent_space was renamed to original_parent_space
This was discussed in http://crrev.com/2679343004

2) While calculating an additional offset for right floats we need to
use float's box size == float's fragment inline size + float's margins
instead of just float's fragment inline size.

3) Fix the calculation of NGFloatingObject::left_offset
(it's used if float is attached to the new parent) for right floats

4) Fix incorrectly attached legacy floating objects.

BUG=635619
TESTS=NGBlockLayoutAlgorithmTest::PositionFloatInsideEmptyBlocks,

Review-Url: https://codereview.chromium.org/2709083002
Cr-Commit-Position: refs/heads/master@{#452189}
4 files changed