Stop TextIterator from emitting double newlines after H1 and H2

TextIterator currently may add two consecutive newlines after an
H1/2 element, while the spec of innerText doesn't have this case at all.

This patch removes the extra newline to make TextIterator more

Most of this patch is rebaselining test results. Only the following
two files contains non-trivial change:
- editing/iterators/TextIterator.cpp: the implementation change
- LayoutTests/TestExpectations: found one more layout tests where
  editing command relying on incorrect plain text char count fails

Bug: 752672,758816
Change-Id: I524ef1e95c9c25372b9ba350e3d70bc5d604985e
Cq-Include-Trybots: master.tryserver.chromium.linux:linux_layout_tests_layout_ng
Reviewed-by: Koji Ishii <>
Reviewed-by: Yoshifumi Inoue <>
Commit-Queue: Xiaocheng Hu <>
Cr-Commit-Position: refs/heads/master@{#501988}
627 files changed