Re-land: Store and restore view focus in OnWindowFocused.

Re-land: Store and restore view focus in OnWindowFocused.

r271281 reverted the first r271249 for Win XP test failures:

http://build.chromium.org/p/chromium.win/builders/XP%20Tests%20%281%29/builds/31239/steps/interactive_ui_tests/logs/stdio
[ RUN      ] ConstrainedWindowViewTest.ClosesOnEscape
[216:3316:0517/130516:ERROR:gpu_info_collector_win.cc(103)] Can't retrieve a valid WinSAT assessment.
c:\b\build\slave\cr-win-rel\build\src\chrome\browser\ui\views\constrained_window_views_browsertest.cc(206): error: Value of: dialog->GetWidget()
  Actual: 08C1F9C0
Expected: 0
Which is: NULL

This CL makes that test no-op on XP; I'll follow up in Issue 177482.

------------------------------------------------------------
Mimic [Desktop]NativeWidgetAura::OnWindowActivated.
Simplify OnNativeBlur calls and OnNative[Blur|Focus] impls.
(View focus changes update the TextInputClient as needed)
Rewrite and enable related ConstrainedWindowViewTests.

Print GetLastError() in SendInput() error case for tests.
(key presses get 5/ERROR_ACCESS_DENIED on locked desktops?)

BUG=368691, 170331, 177482, 163931
TEST=Automated tests; the focused Views change as expected between the browser, web contents, and web content modal dialogs (print preview, collected cookies, etc.).
TBR=sky@chromium.org

Committed: https://src.chromium.org/viewvc/chrome?view=rev&revision=271312

[msw, 2014-05-18 16:33:30]

The CQ bit was checked by msw@chromium.org

[commit-bot: I haz the power, 2014-05-18 16:33:41]

CQ is trying da patch. Follow status at
 https://chromium-status.appspot.com/cq/msw@chromium.org/285403003/20001

[commit-bot: I haz the power, 2014-05-18 19:42:32]

Change committed as 271312