Ensure that NativeWidgetWin::OnPaint calls ValidateRect.

This is a workaround for crbug.com/93530; caused by crrev.com/84823.
Windows creates a WM_PAINT storm without validation; even on empty regions.

BUG=93530
TEST=Issue does not repro; no regressions.

Review URL: http://codereview.chromium.org/8568016

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@110239 0039d316-1c4b-4281-b951-d872f2087c98

views/widget/native_widget_win.cc

@@ -1774,6 +1774,10 @@ void NativeWidgetWin::OnPaint(HDC dc) {
           gfx::CanvasPaint::CreateCanvasPaint(hwnd()));
       delegate_->OnNativeWidgetPaint(canvas->AsCanvas());
     }
+  } else {
+    // TODO(msw): Find a better solution for this crbug.com/93530 workaround.
+    // Some scenarios otherwise fail to validate minimized app/popup windows.
+    ValidateRect(hwnd(), NULL);
   }
 }