Fixes for re-enabling more MSVC level 4 warnings: ui/ edition

Fixes for re-enabling more MSVC level 4 warnings: ui/ edition

This contains fixes for the following sorts of issues:
* Signedness mismatch
* Assignment inside conditional
* Possibly-uninitialized local variable

This also contains a very small number of other cleanups to nearby code.

BUG=81439
TEST=none

Committed: https://src.chromium.org/viewvc/chrome?view=rev&revision=282743

[sky, 2014-07-11 19:09:17]

LGTM

https://codereview.chromium.org/388893003/diff/1/ui/native_theme/native_theme...
File ui/native_theme/native_theme_win.cc (right):

https://codereview.chromium.org/388893003/diff/1/ui/native_theme/native_theme...
ui/native_theme/native_theme_win.cc:1248: const int part_id = extra.is_upper ?
When I come across code with nested ternary operators99% of the time I know it's
written by you;)

[Peter Kasting, 2014-07-11 19:19:55]

https://codereview.chromium.org/388893003/diff/1/ui/native_theme/native_theme...
File ui/native_theme/native_theme_win.cc (right):

https://codereview.chromium.org/388893003/diff/1/ui/native_theme/native_theme...
ui/native_theme/native_theme_win.cc:1248: const int part_id = extra.is_upper ?
On 2014/07/11 19:09:17, sky wrote:
> When I come across code with nested ternary operators99% of the time I know
it's
> written by you;)

As I said in the previous patch, I don't normally prefer these -- I only did it
here for consistency with the other two similar places in this file that already
use these.

The alternative was to do this:

  int part_id = extra.is_upper ? SBP_UPPERTRACKVERT : SBP_LOWERTRACKVERT;
  switch (part) {
    case kScrollbarHorizontalTrack:
      part_id = extra.is_upper ? SBP_UPPERTRACKHORZ : SBP_LOWERTRACKHORZ;
      break;
    case kScrollbarVerticalTrack:
      break;
    default:
      NOTREACHED();
      break;
  }

...which didn't seem sufficiently better to warrant doing this + changing the
other nested ternaries.

Seriously, I stopped preferring nested ternaries about 7 years ago :)

[Peter Kasting, 2014-07-11 19:20:00]

The CQ bit was checked by pkasting@chromium.org

[commit-bot: I haz the power, 2014-07-11 19:21:55]

CQ is trying da patch. Follow status at
 https://chromium-status.appspot.com/cq/pkasting@chromium.org/388893003/1

[commit-bot: I haz the power, 2014-07-12 00:02:13]

Change committed as 282743