add auto SkPMFloat <-> Sk4f conversion

tests/PMFloatTest.cpp

Index: tests/PMFloatTest.cpp
diff --git a/tests/PMFloatTest.cpp b/tests/PMFloatTest.cpp
index 94cd663a5331d5f1a4a8ee3644329491e2647291..f722e80839ab2a20e9cca61b682a4a5131b6d160 100644
--- a/tests/PMFloatTest.cpp
+++ b/tests/PMFloatTest.cpp
@@ -2,6 +2,7 @@
 #include "Test.h"
 
 DEF_TEST(SkPMFloat, r) {
+    // Test SkPMColor <-> SkPMFloat
     SkPMColor c = SkPreMultiplyColor(0xFFCC9933);
 
     SkPMFloat pmf;
@@ -13,6 +14,7 @@ DEF_TEST(SkPMFloat, r) {
 
     REPORTER_ASSERT(r, c == pmf.get());
 
+    // Test clamping.
     SkPMFloat unclamped;
     unclamped.setA(+2.0f);
     unclamped.setR(+0.2f);
@@ -26,4 +28,13 @@ DEF_TEST(SkPMFloat, r) {
     REPORTER_ASSERT(r, SkScalarNearlyEqual(0.2f, clamped.r()));
     REPORTER_ASSERT(r, SkScalarNearlyEqual(0.0f, clamped.g()));
     REPORTER_ASSERT(r, SkScalarNearlyEqual(0.0f, clamped.b()));
+
+    // Test SkPMFloat <-> Sk4f conversion.
+    Sk4f fs = clamped;
+    SkPMFloat scaled = fs.multiply(Sk4f(4,4,4,4));
+
+    REPORTER_ASSERT(r, SkScalarNearlyEqual(4.0f, scaled.a()));
+    REPORTER_ASSERT(r, SkScalarNearlyEqual(0.8f, scaled.r()));
+    REPORTER_ASSERT(r, SkScalarNearlyEqual(0.0f, scaled.g()));
+    REPORTER_ASSERT(r, SkScalarNearlyEqual(0.0f, scaled.b()));
 }