Fix bad pixel address calculation.

BUG=skia:
GOLD_TRYBOT_URL= https://gold.skia.org/search2?unt=true&query=source_type%3Dgm&master=false&issue=1974053002

Review-Url: https://codereview.chromium.org/1974053002
diff --git a/src/core/SkLinearBitmapPipeline_sample.h b/src/core/SkLinearBitmapPipeline_sample.h
index 8171b85..566ed84 100644
--- a/src/core/SkLinearBitmapPipeline_sample.h
+++ b/src/core/SkLinearBitmapPipeline_sample.h
@@ -621,7 +621,7 @@
         , fWidth{srcPixmap.rowBytesAsPixels()} { }
 
     Sk4f getPixelFromRow(const void* row, int index) {
-        const uint32_t* src = static_cast<const uint32_t*>(row);
+        const uint32_t* src = static_cast<const uint32_t*>(row) + index;
         return colorProfile == kSRGB_SkColorProfileType
                ? Sk4f_fromS32(*src)
                : Sk4f_fromL32(*src);
@@ -649,7 +649,7 @@
         , fWidth{srcPixmap.rowBytesAsPixels()} { }
 
     Sk4f getPixelFromRow(const void* row, int index) {
-        const uint32_t* src = static_cast<const uint32_t*>(row);
+        const uint32_t* src = static_cast<const uint32_t*>(row) + index;
         Sk4f pixel = colorProfile == kSRGB_SkColorProfileType
                      ? Sk4f_fromS32(*src)
                      : Sk4f_fromL32(*src);
@@ -695,7 +695,7 @@
     }
 
     Sk4f getPixelFromRow(const void* row, int index) {
-        const uint8_t* src = static_cast<const uint8_t*>(row);
+        const uint8_t* src = static_cast<const uint8_t*>(row) + index;
         Sk4f pixel = fColorTable[*src];
         return pixel;
     }