Everyone gets a namespace {}.

src/core/SkPMFloat.h

 /*
  * Copyright 2015 Google Inc.
  *
  * Use of this source code is governed by a BSD-style license that can be
  * found in the LICENSE file.
  */
 
 #ifndef SkPM_DEFINED
 #define SkPM_DEFINED
 
 #include "SkTypes.h"
 #include "SkColor.h"
 #include "SkColorPriv.h"
 #include "SkNx.h"
 
+// This file may be included multiple times by .cpp files with different flags, leading
+// to different definitions.  Usually that doesn't matter because it's all inlined, but
+// in Debug modes the compilers may not inline everything.  So wrap everything in an
+// anonymous namespace to give each includer their own silo of this code (or the linker
+// will probably pick one randomly for us, which is rarely correct).
+namespace {
+
 // A pre-multiplied color storing each component in the same order as SkPMColor,
 // but as a float in the range [0, 255].
 class SkPMFloat : public Sk4f {
 public:
     static SkPMFloat FromPMColor(SkPMColor c) { return SkPMFloat(c); }
     static SkPMFloat FromARGB(float a, float r, float g, float b) { return SkPMFloat(a,r,g,b); }
 
     // May be more efficient than one at a time.  No special alignment assumed for SkPMColors.
     static void From4PMColors(const SkPMColor[4], SkPMFloat*, SkPMFloat*, SkPMFloat*, SkPMFloat*);
 
@@ skipping 34 matching lines @@
         return this->a() >= 0 && this->a() <= 255
             && this->r() >= 0 && this->r() <= this->a()
             && this->g() >= 0 && this->g() <= this->a()
             && this->b() >= 0 && this->b() <= this->a();
     }
 
 private:
     typedef Sk4f INHERITED;
 };
 
+}  // namespace
+
 #ifdef SKNX_NO_SIMD
     // Platform implementations of SkPMFloat assume Sk4f uses SSE or NEON.  _none is generic.
     #include "../opts/SkPMFloat_none.h"
 #else
     #if SK_CPU_SSE_LEVEL >= SK_CPU_SSE_LEVEL_SSSE3
         #include "../opts/SkPMFloat_SSSE3.h"
     #elif SK_CPU_SSE_LEVEL >= SK_CPU_SSE_LEVEL_SSE2
         #include "../opts/SkPMFloat_SSE2.h"
     #elif defined(SK_ARM_HAS_NEON)
         #include "../opts/SkPMFloat_neon.h"
     #else
         #include "../opts/SkPMFloat_none.h"
     #endif
 #endif
 
 #endif//SkPM_DEFINED