Use the outermost embedder WebContents in ConstrainedWindowMac.

Use the outermost embedder WebContents in ConstrainedWindowMac.

Currently, ConstrainedWindowMac uses the embedder WebContents of the
GuestView if the WebContents is in a GuestView. However, with OOP PDF, a
mime handler view can be embedded in a webview that is embedded in an
app window; in this case, the webview WebContents is used instead of the
app window WebContents. This CL changes ConstrainedWindowMac to use the
outermost embedder WebContents.

This is the same fix as http://crrev.com/321248, but for mac.

BUG=457672
Committed: https://crrev.com/0a61f800e27e0e9a369d27a7e69dc8d9d90fccde
Cr-Commit-Position: refs/heads/master@{#322305}

[Sam McNally, 2015-03-25 00:07:34]

Patchset #1 (id:1) has been deleted

[Sam McNally, 2015-03-25 00:10:31]

sammc@chromium.org changed reviewers:
+ mark@chromium.org

[Mark Mentovai, 2015-03-25 16:13:34]

LGTM

[Mark Mentovai, 2015-03-25 16:14:06]

Be careful with the trybot test failures.

[Sam McNally, 2015-03-26 01:28:29]

The CQ bit was checked by sammc@chromium.org

[commit-bot: I haz the power, 2015-03-26 01:30:20]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/1029583007/20001

[Fady Samuel, 2015-03-26 01:43:01]

fsamuel@chromium.org changed reviewers:
+ fsamuel@chromium.org

[Fady Samuel, 2015-03-26 01:43:02]

https://codereview.chromium.org/1029583007/diff/20001/chrome/browser/ui/cocoa...
File chrome/browser/ui/cocoa/constrained_window/constrained_window_mac.mm
(right):

https://codereview.chromium.org/1029583007/diff/20001/chrome/browser/ui/cocoa...
chrome/browser/ui/cocoa/constrained_window/constrained_window_mac.mm:26: while
(extensions::GuestViewBase* guest_view =
Drive by comment: This pattern has started emerging in a couple of places. I
wonder if it makes sense to put it in GuestViewBase?

It could either be a member method or a static method:

guest->GetTopMostWebContents()

or 

GuestViewBase::GetTopMostWebContents(web_contents)

[commit-bot: I haz the power, 2015-03-26 02:42:32]

Committed patchset #1 (id:20001)

[commit-bot: I haz the power, 2015-03-26 02:43:41]

Patchset 1 (id:??) landed as
https://crrev.com/0a61f800e27e0e9a369d27a7e69dc8d9d90fccde
Cr-Commit-Position: refs/heads/master@{#322305}