Selection API: Fix a null pointer dereference in addRange().

Selection API: Fix a null pointer dereference in addRange().

FrameSelection::firstRange() can be null if the cached Range points invisible
elements.

BUG=694414
Review-Url: https://codereview.chromium.org/2707993004
Cr-Commit-Position: refs/heads/master@{#451954}
Committed: https://chromium.googlesource.com/chromium/src/+/ca0cbc0427aa4c5a60e00ce75a004e44347056eb

[tkent, 2017-02-22 04:29:22]

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

[commit-bot: I haz the power, 2017-02-22 04:30:16]

Dry run: CQ is trying da patch. Follow status at
 
https://chromium-cq-status.appspot.com/v2/patch-status/codereview.chromium.or...

[tkent, 2017-02-22 05:39:45]

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

[tkent, 2017-02-22 05:39:46]

yoichio@, yosin@, would you review this please?

[yosin_UTC9, 2017-02-22 06:31:52]

lgtm

[commit-bot: I haz the power, 2017-02-22 07:35:07]

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

[commit-bot: I haz the power, 2017-02-22 07:35:07]

Dry run: Try jobs failed on following builders:
  linux_chromium_asan_rel_ng on master.tryserver.chromium.linux (JOB_FAILED,
http://build.chromium.org/p/tryserver.chromium.linux/builders/linux_chromium_...)

[tkent, 2017-02-22 07:36:08]

The CQ bit was checked by tkent@chromium.org

[commit-bot: I haz the power, 2017-02-22 07:36:56]

CQ is trying da patch. Follow status at
 
https://chromium-cq-status.appspot.com/v2/patch-status/codereview.chromium.or...

[commit-bot: I haz the power, 2017-02-22 09:28:10]

CQ is committing da patch.

Bot data: {"patchset_id": 1, "attempt_start_ts": 1487748968241900, "parent_rev":
"000906e1a0fda481542568624e4c280d52acdce0", "commit_rev":
"ca0cbc0427aa4c5a60e00ce75a004e44347056eb"}

[commit-bot: I haz the power, 2017-02-22 09:28:55]

Description was changed from

==========
Selection API: Fix a null pointer dereference in addRange().

FrameSelection::firstRange() can be null if the cached Range points invisible
elements.

BUG=694414
==========

to

==========
Selection API: Fix a null pointer dereference in addRange().

FrameSelection::firstRange() can be null if the cached Range points invisible
elements.

BUG=694414

Review-Url: https://codereview.chromium.org/2707993004
Cr-Commit-Position: refs/heads/master@{#451954}
Committed:
https://chromium.googlesource.com/chromium/src/+/ca0cbc0427aa4c5a60e00ce75a00...
==========

[commit-bot: I haz the power, 2017-02-22 09:29:01]

Committed patchset #1 (id:1) as
https://chromium.googlesource.com/chromium/src/+/ca0cbc0427aa4c5a60e00ce75a00...