SkPMFloat: avoid loads and stores where possible.

src/opts/SkPMFloat_none.h

Index: src/opts/SkPMFloat_none.h
diff --git a/src/opts/SkPMFloat_none.h b/src/opts/SkPMFloat_none.h
index a33fa7a28d91e6d2068ee4ab77c427d90bcafc30..c47f8a37132b28c7692acc804fe0e3bf0dc89fc5 100644
--- a/src/opts/SkPMFloat_none.h
+++ b/src/opts/SkPMFloat_none.h
@@ -1,4 +1,7 @@
-#include "SkColorPriv.h"
+inline SkPMFloat& SkPMFloat::operator=(const SkPMFloat& that) {
+    for (int i = 0; i < 4; i++) { fColor[i] = that.fColor[i]; }
+    return *this;
+}
 
 inline SkPMFloat::SkPMFloat(SkPMColor c) {
     *this = SkPMFloat::FromARGB(SkGetPackedA32(c),