Move const PortName data out of header file

Move const PortName data out of header file

When non-integral const data is defined in a header file it often ends
up being instantiated in multiple translation units. It also ends up in
the read/write data segment which means it isn't shared between
processes. This change has the following affect on the size of sections
in a 32-bit release Windows build:

chrome.dll
     .text:  -128 bytes change
    .rdata:    64 bytes change
     .data:  -800 bytes change
    .reloc:   -12 bytes change
Total change:  -876 bytes

chrome_child.dll
     .text:    64 bytes change
    .rdata:    48 bytes change
     .data:  -800 bytes change
    .reloc:   -68 bytes change
Total change:  -756 bytes

Note that the sections that increase in size are shareable.

The technique of using static constexpr in a struct is the only way to
guarantee both zero duplication of data and no run-time construction
of data (until C++17 and inline variables).

BUG=630755

[brucedawson, 2016-11-17 19:10:06]

The CQ bit was checked by brucedawson@chromium.org to run a CQ dry run

[commit-bot: I haz the power, 2016-11-17 19:11:34]

Dry run: CQ is trying da patch. Follow status at
 
https://chromium-cq-status.appspot.com/v2/patch-status/codereview.chromium.or...

[commit-bot: I haz the power, 2016-11-17 20:29:11]

The CQ bit was unchecked by commit-bot@chromium.org

[commit-bot: I haz the power, 2016-11-17 20:29:13]

Dry run: Try jobs failed on following builders:
  win_chromium_x64_rel_ng on master.tryserver.chromium.win (JOB_FAILED,
http://build.chromium.org/p/tryserver.chromium.win/builders/win_chromium_x64_...)

[brucedawson, 2016-11-21 23:12:40]

On 2016/11/17 20:29:13, commit-bot: I haz the power wrote:
> Dry run: Try jobs failed on following builders:
>   win_chromium_x64_rel_ng on master.tryserver.chromium.win (JOB_FAILED,
>
http://build.chromium.org/p/tryserver.chromium.win/builders/win_chromium_x64_...)

crrev.com/2515483002 is a simpler fix for this issue. It is theoretically not as
good but in practice seems to work as well or better. Closing this CL.