Fix threading issue in DirectWrite port initialization.

Fix threading issue in DirectWrite port initialization.

The DirectWrite port maintains a global instance of an IDWriteFactory,
which is used to create all other DirectWrite objects. However, the
initialization of this object is not currently thread safe.

R=caryclark@google.com

Committed: https://code.google.com/p/skia/source/detail?r=12573

[bungeman-skia, 2013-12-09 18:08:34]

Note that this changed the return type of get_dwrite_factory, so the call sites
are updated. The return value is checked in cases that can be called directly.
The return value is asserted when it should be impossible to get to that
location in the code if the factory were not available.

[caryclark, 2013-12-09 18:45:50]

lgtm -- no need to fix formatting nits

https://codereview.chromium.org/107963003/diff/1/src/ports/SkFontHost_win_dw.cpp
File src/ports/SkFontHost_win_dw.cpp (right):

https://codereview.chromium.org/107963003/diff/1/src/ports/SkFontHost_win_dw....
src/ports/SkFontHost_win_dw.cpp:86: ;
I know this is old code, but I find the indention very strange. Do we do this in
other places in Skia?

https://codereview.chromium.org/107963003/diff/1/src/ports/SkFontHost_win_dw....
src/ports/SkFontHost_win_dw.cpp:98: "Could not create DirectWrite factory.");
More unusual indention

[bungeman-skia, 2013-12-09 18:57:51]

https://codereview.chromium.org/107963003/diff/1/src/ports/SkFontHost_win_dw.cpp
File src/ports/SkFontHost_win_dw.cpp (right):

https://codereview.chromium.org/107963003/diff/1/src/ports/SkFontHost_win_dw....
src/ports/SkFontHost_win_dw.cpp:86: ;
On 2013/12/09 18:45:50, caryclark wrote:
> I know this is old code, but I find the indention very strange. Do we do this
in
> other places in Skia?

Probably not. I think the idea was to put the closer of multi-line expressions
at the same indentation as the opener. It just makes the expressions look like
blocks. Modified now that we have more space and we can get away with fewer
indentation levels.

https://codereview.chromium.org/107963003/diff/1/src/ports/SkFontHost_win_dw....
src/ports/SkFontHost_win_dw.cpp:98: "Could not create DirectWrite factory.");
On 2013/12/09 18:45:50, caryclark wrote:
> More unusual indention

Not sure this is that unusual, the HRVM macro takes two arguments, an expression
and a string. The string here is just the second argument, so it lines up with
the first argument.

[bungeman-skia, 2013-12-09 18:58:33]

Committed patchset #2 manually as r12573 (presubmit successful).