Set attached flag before we call didAddScrollbar

Set attached flag before we call didAddScrollbar

This issue is caused by we call didAddScrollbar before set the attached flag.
That makes FrameView::horizontalScrollbar, FrameView::verticalScrollbar
always return null and ScrollableArea::setScrollbarOverlayColorTheme can not set
OverlayColorTheme to ScrollbarThemeMac.

In this patch we move the attached flag set before didAddScrollbar call.

BUG=688516
Review-Url: https://codereview.chromium.org/2671323004
Cr-Commit-Position: refs/heads/master@{#448814}
(cherry picked from commit b45a817c9a86d2d25ed6fba359abceafc728c2d3)

Review-Url: https://codereview.chromium.org/2686713005 .
Cr-Commit-Position: refs/branch-heads/2987@{#407}
Cr-Branched-From: ad51088c0e8776e8dcd963dbe752c4035ba6dab6-refs/heads/master@{#444943}
Committed: https://chromium.googlesource.com/chromium/src/+/f8c54e0176fb6c3f9b31e5dbfcfd8d727df8d500

[bokan, 2017-02-09 16:17:56]

Description was changed from

==========
Set attached flag before we call didAddScrollbar

This issue is caused by we call didAddScrollbar before set the attached flag.
That makes FrameView::horizontalScrollbar, FrameView::verticalScrollbar
always return null and ScrollableArea::setScrollbarOverlayColorTheme can not set
OverlayColorTheme to ScrollbarThemeMac.

In this patch we move the attached flag set before didAddScrollbar call.

BUG=688516

Review-Url: https://codereview.chromium.org/2671323004
Cr-Commit-Position: refs/heads/master@{#448814}
(cherry picked from commit b45a817c9a86d2d25ed6fba359abceafc728c2d3)
==========

to

==========
Set attached flag before we call didAddScrollbar

This issue is caused by we call didAddScrollbar before set the attached flag.
That makes FrameView::horizontalScrollbar, FrameView::verticalScrollbar
always return null and ScrollableArea::setScrollbarOverlayColorTheme can not set
OverlayColorTheme to ScrollbarThemeMac.

In this patch we move the attached flag set before didAddScrollbar call.

BUG=688516

Review-Url: https://codereview.chromium.org/2671323004
Cr-Commit-Position: refs/heads/master@{#448814}
(cherry picked from commit b45a817c9a86d2d25ed6fba359abceafc728c2d3)

Review-Url: https://codereview.chromium.org/2686713005 .
Cr-Commit-Position: refs/branch-heads/2987@{#407}
Cr-Branched-From:
ad51088c0e8776e8dcd963dbe752c4035ba6dab6-refs/heads/master@{#444943}
Committed:
https://chromium.googlesource.com/chromium/src/+/f8c54e0176fb6c3f9b31e5dbfcfd...
==========

[bokan, 2017-02-09 16:17:57]

Committed patchset #1 (id:1) manually as
f8c54e0176fb6c3f9b31e5dbfcfd8d727df8d500.