Add a constructor to TextIterator taking two Positions as iteration range.

Add a constructor to TextIterator taking two Positions as iteration range.

This refactoring patch is a step towards fixing a bug in the find-in-page
functionality. To fix the issue, we need a way to pass a document range
which may span multiple TreeScopes to findPlainText() (and eventually
TextIterator). Currently it takes a Range, which does not support this kind
of document ranges.

This patch introduces an overloaded constructor of TextIterator taking
two Positions instead of a Range. The core routine of the old constructor
is moved to a private member function so that it can be shared with
different constructors.

This patch also moves some obvious initialization of member variables in
the constructor body to the initializer list.

No behavior change expected.

BUG=353430
Committed: https://src.chromium.org/viewvc/blink?view=rev&revision=170002

[yosin_UTC9, 2014-03-26 01:08:02]

LGTM!

This patch is so cool and I'm excited. This patch gives us practical example of
how to define range spanning among DOM tree.

https://codereview.chromium.org/210363006/diff/1/Source/core/editing/TextIter...
File Source/core/editing/TextIterator.cpp (right):

https://codereview.chromium.org/210363006/diff/1/Source/core/editing/TextIter...
Source/core/editing/TextIterator.cpp:298: , m_entersAuthorShadowRoots(behavior &
TextIteratorEntersAuthorShadowRoots)
Once Blink incorporate C++11 delegating constructors, we would like to use it
here. ;-)

[Yuta Kitamura, 2014-03-26 01:58:58]

https://codereview.chromium.org/210363006/diff/1/Source/core/editing/TextIter...
File Source/core/editing/TextIterator.cpp (right):

https://codereview.chromium.org/210363006/diff/1/Source/core/editing/TextIter...
Source/core/editing/TextIterator.cpp:298: , m_entersAuthorShadowRoots(behavior &
TextIteratorEntersAuthorShadowRoots)
On 2014/03/26 01:08:02, Yoshi wrote:
> Once Blink incorporate C++11 delegating constructors, we would like to use it
> here. ;-)

Yup; actually this long initializer list is kind of silly.

[Yuta Kitamura, 2014-03-26 01:59:01]

The CQ bit was checked by yutak@chromium.org

[commit-bot: I haz the power, 2014-03-26 01:59:07]

CQ is trying da patch. Follow status at
https://chromium-status.appspot.com/cq/yutak@chromium.org/210363006/1

[commit-bot: I haz the power, 2014-03-26 02:07:58]

Change committed as 170002