[md] Give each infobar its own layer.

[md] Give each infobar its own layer.

This is necessary so latter bars can draw their arrow above the previous bar.
This is similar to crbug.com/589771 , the fix for which only worked for the first infobar.

This also fixes hit testing which was broken when there was a floating bookmark bar below the infobar.

BUG=592727, 593640
Review URL: https://codereview.chromium.org/1767363002

Cr-Commit-Position: refs/heads/master@{#381267}
(cherry picked from commit 966e15221d7c60c7922d94af047a6663cb175c1e)

Committed: https://chromium.googlesource.com/chromium/src/+/f4ee21f5b2c49c57ca897b85c1ed67b375ad2603

[Evan Stade, 2016-03-18 18:35:45]

The CQ bit was checked by estade@chromium.org

[Evan Stade, 2016-03-18 18:35:51]

The CQ bit was unchecked by estade@chromium.org

[Evan Stade, 2016-03-18 18:40:01]

Description was changed from

==========
[md] Give each infobar its own layer.

This is necessary so latter bars can draw their arrow above the previous bar.
This is similar to crbug.com/589771 , the fix for which only worked for the
first infobar.

This also fixes hit testing which was broken when there was a floating bookmark
bar below the infobar.

BUG=592727, 593640

Review URL: https://codereview.chromium.org/1767363002

Cr-Commit-Position: refs/heads/master@{#381267}
(cherry picked from commit 966e15221d7c60c7922d94af047a6663cb175c1e)
==========

to

==========
[md] Give each infobar its own layer.

This is necessary so latter bars can draw their arrow above the previous bar.
This is similar to crbug.com/589771 , the fix for which only worked for the
first infobar.

This also fixes hit testing which was broken when there was a floating bookmark
bar below the infobar.

BUG=592727, 593640

Review URL: https://codereview.chromium.org/1767363002

Cr-Commit-Position: refs/heads/master@{#381267}
(cherry picked from commit 966e15221d7c60c7922d94af047a6663cb175c1e)

Committed:
https://chromium.googlesource.com/chromium/src/+/f4ee21f5b2c49c57ca897b85c1ed...
==========

[Evan Stade, 2016-03-18 18:40:03]

Committed patchset #1 (id:1) manually as
f4ee21f5b2c49c57ca897b85c1ed67b375ad2603.