Support Float32 output from SkColorSpaceXform

* Adds Float32 support to SkColorSpaceXform
* Changes API to allows clients to ask for F32, updates clients to
  new API
* Adds Sk4f_load4 and Sk4f_store4 to SkNx
* Make use of new xform in SkGr.cpp

BUG=skia:
GOLD_TRYBOT_URL= https://gold.skia.org/search?issue=2339233003
CQ_INCLUDE_TRYBOTS=master.client.skia:Test-Ubuntu-GCC-GCE-CPU-AVX2-x86_64-Release-SKNX_NO_SIMD-Trybot

Committed: https://skia.googlesource.com/skia/+/43d6651111374b5d1e4ddd9030dcf079b448ec47
Review-Url: https://codereview.chromium.org/2339233003
diff --git a/tests/SkNxTest.cpp b/tests/SkNxTest.cpp
index 51d937d..a3aef6b 100644
--- a/tests/SkNxTest.cpp
+++ b/tests/SkNxTest.cpp
@@ -307,3 +307,35 @@
         REPORTER_ASSERT(r, expected == actual);
     }
 }
+
+DEF_TEST(SkNx_4fLoad4Store4, r) {
+    float src[] = {
+         0.0f,  1.0f,  2.0f,  3.0f,
+         4.0f,  5.0f,  6.0f,  7.0f,
+         8.0f,  9.0f, 10.0f, 11.0f,
+        12.0f, 13.0f, 14.0f, 15.0f
+    };
+
+    Sk4f a, b, c, d;
+    Sk4f_load4(src, &a, &b, &c, &d);
+    REPORTER_ASSERT(r,  0.0f == a[0]);
+    REPORTER_ASSERT(r,  4.0f == a[1]);
+    REPORTER_ASSERT(r,  8.0f == a[2]);
+    REPORTER_ASSERT(r, 12.0f == a[3]);
+    REPORTER_ASSERT(r,  1.0f == b[0]);
+    REPORTER_ASSERT(r,  5.0f == b[1]);
+    REPORTER_ASSERT(r,  9.0f == b[2]);
+    REPORTER_ASSERT(r, 13.0f == b[3]);
+    REPORTER_ASSERT(r,  2.0f == c[0]);
+    REPORTER_ASSERT(r,  6.0f == c[1]);
+    REPORTER_ASSERT(r, 10.0f == c[2]);
+    REPORTER_ASSERT(r, 14.0f == c[3]);
+    REPORTER_ASSERT(r,  3.0f == d[0]);
+    REPORTER_ASSERT(r,  7.0f == d[1]);
+    REPORTER_ASSERT(r, 11.0f == d[2]);
+    REPORTER_ASSERT(r, 15.0f == d[3]);
+
+    float dst[16];
+    Sk4f_store4(dst, a, b, c, d);
+    REPORTER_ASSERT(r, 0 == memcmp(dst, src, 16 * sizeof(float)));
+}