[FCP++] TextPaint: Move node checking from pre-paint to paint

Currently FCP++ is hooking into pre-paint-tree-walk for node-checking.
FCP++ is supposed to check the nodes to be painted immediately
afterwards. However, pre-paint-tree-walk will expose more than the
nodes FCP++ need to know. As an improvement, we are going to move
node-checking to painter::paint.

We've changed the visual rect of an object. Originally, we used
object.FirstFragment().VisualRect(). Now we change to use
object.FragmentsVisualRectBoundingBox().

Bug: 924301
Change-Id: If8d65ace02ce400334803db0dbde2b85f3c182f5
Reviewed-on: https://chromium-review.googlesource.com/c/1427794
Commit-Queue: Liquan (Max) Gu <maxlg@chromium.org>
Reviewed-by: Xianzhu Wang <wangxianzhu@chromium.org>
Cr-Commit-Position: refs/heads/master@{#631304}
11 files changed