Refactor to put SkXfermode_opts inside SK_OPTS_NS.

Without this refactor I was getting warnings previously about having code
inside namespace SK_OPTS_NS (e.g. namespace sse2, namespace neon) referring to
code inside an anonymous namespace (Sk4px, SkPMFloat, Sk4f, etc) [1].

That low-level code was in an anonymous namespace to allow multiple independent
copies of its methods to be instantiated without the linker getting confused /
offended about violating the One Definition Rule.  This was only happening in
Debug mode where the methods were not being inlined.

To fix this all, I've force-inlined the methods of the low-level code and
removed the anonymous namespace.

BUG=skia:4117

[1] Here is what those errors looked like:

In file included from ../../../../src/core/SkOpts.cpp:18:0:
../../../../src/opts/SkXfermode_opts.h:193:7: error: 'portable::Sk4pxXfermode' has a field 'portable::Sk4pxXfermode::fProc4' whose type uses the anonymous namespace [-Werror]
 class Sk4pxXfermode : public SkProcCoeffXfermode {
       ^
../../../../src/opts/SkXfermode_opts.h:193:7: error: 'portable::Sk4pxXfermode' has a field 'portable::Sk4pxXfermode::fAAProc4' whose type uses the anonymous namespace [-Werror]
../../../../src/opts/SkXfermode_opts.h:235:7: error: 'portable::SkPMFloatXfermode' has a field 'portable::SkPMFloatXfermode::fProcF' whose type uses the anonymous namespace [-Werror]
 class SkPMFloatXfermode : public SkProcCoeffXfermode {
       ^
cc1plus: all warnings being treated as errors

Review URL: https://codereview.chromium.org/1286093004

1 files changed, 2 insertions, 2 deletions

diff --git a/src/opts/SkXfermode_opts.h b/src/opts/SkXfermode_opts.h
index e5ca257a28..5394e636e7 100644
--- a/src/opts/SkXfermode_opts.h
+++ b/src/opts/SkXfermode_opts.h
@@ -12,7 +12,7 @@
 #include "SkPMFloat.h"
 #include "SkXfermode_proccoeff.h"
 
-namespace /* TODO: SK_OPTS_NS */ {
+namespace SK_OPTS_NS {
 
 // Most xfermodes can be done most efficiently 4 pixels at a time in 8 or 16-bit fixed point.
 #define XFERMODE(Name) static Sk4px SK_VECTORCALL Name(Sk4px s, Sk4px d)
@@ -274,7 +274,7 @@ private:
     typedef SkProcCoeffXfermode INHERITED;
 };
 
-static SkXfermode* SkCreate4pxXfermode(const ProcCoeff& rec, SkXfermode::Mode mode) {
+static SkXfermode* create_xfermode(const ProcCoeff& rec, SkXfermode::Mode mode) {
     switch (mode) {
     #define CASE(Mode) case SkXfermode::k##Mode##_Mode: \
         return SkNEW_ARGS(Sk4pxXfermode, (rec, mode, &Mode, &xfer_aa<Mode>))