Use |FrameSelection::selectedText()| where possible.

Use |FrameSelection::selectedText()| where possible.

Partially reland https://codereview.chromium.org/1377963004/,
except for changes in |WebLocalFrameImpl::selectionAsText()|.

Substitute occurrences of selection -> range -> (text or html) conversions with
direct selection -> (text or html) conversions using existing functions.

BUG=545746
Committed: https://crrev.com/a728430c10449ebafdc4ca4eece40c40ec2b07a1
Cr-Commit-Position: refs/heads/master@{#357309}

[kotenkov, 2015-11-01 08:26:53]

kotenkov@yandex-team.ru changed reviewers:
+ yosin@chromium.org

[kotenkov, 2015-11-01 08:26:54]

Hello, Yosin!
Sorry for the delay. I've split the changes in two patches as you suggested
here: https://codereview.chromium.org/1412713003/#msg32 .
This patch contains most of the changes, except for the changes in
|WebLocalFrameImpl::selectionAsText()| and HTMLTextFormControlElement.cpp. I'm
going to create the second cl when this one lands.
Would you please take a look and run try jobs for me as usual?

[yosin_UTC9, 2015-11-02 03:47:18]

The CQ bit was checked by yosin@chromium.org to run a CQ dry run

[commit-bot: I haz the power, 2015-11-02 03:47:36]

Dry run: CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/1427733003/1
View timeline at
 https://chromium-cq-status.appspot.com/patch-timeline/1427733003/1

[yosin_UTC9, 2015-11-02 03:48:23]

yosin@chromium.org changed reviewers:
+ tkent@chromium.org

[yosin_UTC9, 2015-11-02 03:48:24]

lgtm

+tkent@ for OWNERS review.

[tkent, 2015-11-02 04:58:33]

lgtm

[commit-bot: I haz the power, 2015-11-02 05:21:45]

The CQ bit was unchecked by commit-bot@chromium.org

[commit-bot: I haz the power, 2015-11-02 05:21:46]

Dry run: This issue passed the CQ dry run.

[kotenkov, 2015-11-02 05:49:02]

The CQ bit was checked by kotenkov@yandex-team.ru

[commit-bot: I haz the power, 2015-11-02 05:49:21]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/1427733003/1
View timeline at
 https://chromium-cq-status.appspot.com/patch-timeline/1427733003/1

[commit-bot: I haz the power, 2015-11-02 05:53:29]

Committed patchset #1 (id:1)

[commit-bot: I haz the power, 2015-11-02 05:54:19]

Patchset 1 (id:??) landed as
https://crrev.com/a728430c10449ebafdc4ca4eece40c40ec2b07a1
Cr-Commit-Position: refs/heads/master@{#357309}