Mac/Linux: Ensure window size constraints propagate to the window server during Init

Mac/Linux: Ensure window size constraints propagate to the window server during Init

Currently fixed-size views dialogs on Mac don't initialize properly.
(And, e.g., WebDialogBrowserTest.SizeWindow fails because of it).
Desktop Linux has a similar issue.

On desktop Linux, NativeWidgetPrivate::OnRootViewLayout triggers a call
to UpdateMinAndMaxSize. OnRootViewLayout happens during Widget::Init()
but the X11 window is not yet mapped, so this was resulting in a no-op.
For Linux, fix by explicitly calling UpdateMinAndMaxSize after the
window is mapped.

Mac needs to do a similar thing during Init. However, Mac was calling
OnSizeConstraintsChanged() before Widget::Init() had set the non-client
view, so Widget::GetMinimumSize() returned invalid sizes. For Mac, move
the OnSizeConstraintsChanged() call to OnRootViewLayout(), similar to
Linux.

Then, add a cross-platform test. Mac was not clamping to the size
constraints in SetBounds(), so do that.

For the test itself, collapse the testing WidgetDelegates in
widget_unittest.cc into one helper class rather than adding yet another
WidgetDelegate. Then, provide a way to query the OS for the minimum
window size to fill the gaps required for testing the propagation of
size constraints to the window server.

BUG=454698, 447086
Committed: https://crrev.com/c07049637a2deb72869370136c85d70ac608a91a
Cr-Commit-Position: refs/heads/master@{#325538}

[tapted, 2015-04-15 09:06:01]

Patchset #3 (id:40001) has been deleted

[tapted, 2015-04-15 09:32:42]

Patchset #4 (id:80001) has been deleted

[tapted, 2015-04-16 05:09:02]

Patchset #5 (id:120001) has been deleted

[tapted, 2015-04-16 05:09:12]

Patchset #6 (id:160001) has been deleted

[tapted, 2015-04-16 08:52:41]

tapted@chromium.org changed reviewers:
+ erg@chromium.org, sky@chromium.org

[tapted, 2015-04-16 08:52:42]

Hi sky - please take a look
erg - please take a look for the desktop_window_tree_host_x11.cc change

Thanks!

[Elliot Glaysher, 2015-04-16 18:02:31]

x11 stuff lgtm

[sky, 2015-04-16 19:15:08]

LGTM

[tapted, 2015-04-16 23:02:05]

The CQ bit was checked by tapted@chromium.org

[commit-bot: I haz the power, 2015-04-16 23:04:23]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/1059853007/220001

[commit-bot: I haz the power, 2015-04-16 23:10:32]

Committed patchset #8 (id:220001)

[commit-bot: I haz the power, 2015-04-16 23:11:27]

Patchset 8 (id:??) landed as
https://crrev.com/c07049637a2deb72869370136c85d70ac608a91a
Cr-Commit-Position: refs/heads/master@{#325538}