Everyone gets a namespace {}.

src/core/SkPMFloat.h

Index: src/core/SkPMFloat.h
diff --git a/src/core/SkPMFloat.h b/src/core/SkPMFloat.h
index eb575f2ee4520b92c204ad2bdde8e6bd7f1b0857..ce7b75e705f002c91c224e53f077e72e16d0b7c3 100644
--- a/src/core/SkPMFloat.h
+++ b/src/core/SkPMFloat.h
@@ -13,6 +13,13 @@
 #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 {
@@ -67,6 +74,8 @@ 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"