Fix a couple panel overflow related bugs.

Fix a couple panel overflow related bugs.
1) Moving mouse to left screen edge causes the expanded overflow panels to shrink back.
2) Overflow panel is brought to normal area cannot be dragged correctly.

BUG=106434
TEST=Enable overflow test plus manual test by moving mouse to left screen edge or clicking on overflow panel

Committed: http://src.chromium.org/viewvc/chrome?view=rev&revision=113053

[jennb, 2011-12-05 21:20:09]

LGTM if try bots are happy.

http://codereview.chromium.org/8802021/diff/1/chrome/browser/ui/panels/panel_...
File chrome/browser/ui/panels/panel_browsertest.cc (left):

http://codereview.chromium.org/8802021/diff/1/chrome/browser/ui/panels/panel_...
chrome/browser/ui/panels/panel_browsertest.cc:124: EXPECT_EQ(Panel::IN_OVERFLOW,
panel4->expansion_state());
Probably ok to leave these lines in. especially line 133 to make sure that
panel5 going to overflow did not affect panel4's state.

http://codereview.chromium.org/8802021/diff/1/chrome/browser/ui/panels/panel_...
File chrome/browser/ui/panels/panel_browsertest.cc (right):

http://codereview.chromium.org/8802021/diff/1/chrome/browser/ui/panels/panel_...
chrome/browser/ui/panels/panel_browsertest.cc:552: #if defined(OS_WIN)
Can you put a comment here referencing the bug # that overflow is only enabled
for Win right now?

http://codereview.chromium.org/8802021/diff/1/chrome/browser/ui/panels/panel_...
File chrome/browser/ui/panels/panel_strip.cc (right):

http://codereview.chromium.org/8802021/diff/1/chrome/browser/ui/panels/panel_...
chrome/browser/ui/panels/panel_strip.cc:102:
panel->SetExpansionState(Panel::EXPANDED);
Move this after line 104. Seems better than putting this in the middle of bounds
calculations as SetExpansionState also results in bounds calculations.

http://codereview.chromium.org/8802021/diff/1/chrome/browser/ui/panels/panel_...
chrome/browser/ui/panels/panel_strip.cc:153: panels_.push_back(panel);
Add DCHECK before this line that expansion state is EXPANDED.

[jianli, 2011-12-05 23:05:38]

All Jenn's feedbacks have been addressed.

I only ran panel related tests for WIN try bot.

WIN: http://build.chromium.org/p/tryserver.chromium/builders/win/builds/6706

MAC: http://build.chromium.org/p/tryserver.chromium/builders/linux/builds/6371