Editing: Fix a crash in FrameSelection::invalidateCaretRect.

Node::renderer() can be null and invalidateLocalCaretRect(node->renderer()) calls
a renderer function. It causes crash.
CaretBase::repaintCaretForLocalRect(node) invalidates a rectangle in renderer
 if renderer is not null. It does not repaint but invalidate so I rename it to 
invalidateLocalCaretRect.

Call that CaretBase::invalidateLocalCaretRect instead of invalidateLocalCaretRect,


BUG=404553

Review URL: https://codereview.chromium.org/495903002

git-svn-id: svn://svn.chromium.org/blink/trunk@180941 bbb929c8-8fbe-4397-9dbb-9b2b20218538