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

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

This contains fixes for the following sorts of issues:
* Signedness mismatch

This relies on https://codereview.chromium.org/376003003 to make FPDF_FillRect()
take a 32-bit value for the color in order to make the changes here as simple
and clean as possible.

This also contains a few other cleanups to make code simpler or more consistent.

BUG=81439
TEST=none

Committed: https://src.chromium.org/viewvc/chrome?view=rev&revision=282146

[Peter Kasting, 2014-07-08 21:28:25]

https://codereview.chromium.org/372273005/diff/1/pdf/instance.h
File pdf/instance.h (right):

https://codereview.chromium.org/372273005/diff/1/pdf/instance.h#newcode231
pdf/instance.h:231: void FillRect(const pp::Rect& rect, uint32 color);
The changes from unsigned int to uint32 in this CL are just to get better type
agreement everywhere, so we aren't using one in some places and the other in
others.

https://codereview.chromium.org/372273005/diff/1/pdf/pdf_engine.h
File pdf/pdf_engine.h (right):

https://codereview.chromium.org/372273005/diff/1/pdf/pdf_engine.h#newcode32
pdf/pdf_engine.h:32: const uint32 kBackgroundColor = 0xFFCCCCCC;
The old #defines treated the relevant values as signed, which caused signedness
mismatches when combining them into a uint32.  Using a const uint32 instead of a
macro for this kind of thing both solves this problem and makes a variety of
places shorter, but requires a pdfium change.

[Lei Zhang, 2014-07-08 22:00:42]

lgtm assuming the pdfium side change is ok.

[Bo Xu, 2014-07-08 22:32:53]

On 2014/07/08 22:00:42, Lei Zhang wrote:
> lgtm assuming the pdfium side change is ok.

The changes lgtm.

[Lei Zhang, 2014-07-09 18:48:15]

You can roll DEPS for pdfium to 532a6a7ece21ca4ea253a196bb5c61a1861d12a0 in this
CL. It also brings in d573678115676fc06575d6dac0801a3532cf0216 which is a small
bug fix.

[Peter Kasting, 2014-07-09 21:40:00]

The CQ bit was checked by pkasting@chromium.org

[commit-bot: I haz the power, 2014-07-09 21:42:28]

CQ is trying da patch. Follow status at
 https://chromium-status.appspot.com/cq/pkasting@chromium.org/372273005/20001

[commit-bot: I haz the power, 2014-07-09 22:24:44]

Change committed as 282146