Everyone gets a namespace {}.

src/opts/SkPMFloat_SSE2.h

Index: src/opts/SkPMFloat_SSE2.h
diff --git a/src/opts/SkPMFloat_SSE2.h b/src/opts/SkPMFloat_SSE2.h
index 88a38039b507dc7fe593e62f5b01f99237d5d96b..c7e791ff62c89299d9823fde0d2c2f66fd353349 100644
--- a/src/opts/SkPMFloat_SSE2.h
+++ b/src/opts/SkPMFloat_SSE2.h
@@ -5,6 +5,8 @@
  * found in the LICENSE file.
  */
 
+namespace {  // See SkPMFloat.h
+
 // For SkPMFloat(SkPMColor), we widen our 8 bit components (fix8) to 8-bit components in 16 bits
 // (fix8_16), then widen those to 8-bit-in-32-bits (fix8_32), and finally convert those to floats.
 
@@ -78,3 +80,5 @@ inline void SkPMFloat::RoundClampTo4PMColors(
     SkPMColorAssert(colors[2]);
     SkPMColorAssert(colors[3]);
 }
+
+}  // namespace