Fix BC1 SW decompression on platforms with RGBA PM color order

Bug: skia:9680
Change-Id: Ibe802ea574d749ebd601118d0e6da32b2a18fab2
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/268619
Reviewed-by: Brian Osman <brianosman@google.com>
Commit-Queue: Robert Phillips <robertphillips@google.com>
diff --git a/src/core/SkCompressedDataUtils.cpp b/src/core/SkCompressedDataUtils.cpp
index 5c9d14a..3f7dc58 100644
--- a/src/core/SkCompressedDataUtils.cpp
+++ b/src/core/SkCompressedDataUtils.cpp
@@ -190,7 +190,7 @@
 
             colors[0] = from565(curBlock->fColor0);
             colors[1] = from565(curBlock->fColor1);
-            if (colors[0] <= colors[1]) {                 // signal for a transparent block
+            if (curBlock->fColor0 <= curBlock->fColor1) {        // signal for a transparent block
                 colors[2] = SkPackARGB32(
                     0xFF,
                     (SkGetPackedR32(colors[0]) + SkGetPackedR32(colors[1])) >> 1,