Publicly expose one accelerated swizzle.

SkOpts is intentionally internal, but we want to give Chrome access
to those pieces that would seriously benefit them.
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Review URL: https://codereview.chromium.org/1822363002
diff --git a/tests/SwizzlerTest.cpp b/tests/SwizzlerTest.cpp
index e1626d5..1b34669 100644
--- a/tests/SwizzlerTest.cpp
+++ b/tests/SwizzlerTest.cpp
@@ -5,6 +5,7 @@
  * found in the LICENSE file.
  */
 
+#include "SkSwizzle.h"
 #include "SkSwizzler.h"
 #include "Test.h"
 #include "SkOpts.h"
@@ -157,3 +158,12 @@
     SkOpts::RGBA_to_bgrA(&dst, &src, 1);
     REPORTER_ASSERT(r, dst == 0xFA04ADCA);
 }
+
+DEF_TEST(PublicSwizzleOpts, r) {
+    uint32_t dst, src;
+
+    // check a totally arbitrary color
+    src = 0xFACEB004;
+    SkSwapRB(&dst, &src, 1);
+    REPORTER_ASSERT(r, dst == 0xFA04B0CE);
+}