[Layout API] Use FrameView::layoutViewItem() in WebPluginContainerImpl.cpp

There are several references to layoutView() which can be replaced
1-1 with layoutViewItem(). I had to add a localToAbsoluteQuad() method
to LayoutItem.

BUG=499321

Review-Url: https://codereview.chromium.org/1994443003
Cr-Commit-Position: refs/heads/master@{#405653}
2 files changed