fix emoji clipping in hw draw path

I guess we don't want to overwrite the last line in every RGBA glyph
with our one-line texture atlas spacer?

Bug: 10841207
Change-Id: Ief85ca58650c731e9d21dbf90942b7b44670abcc
diff --git a/libs/hwui/FontRenderer.cpp b/libs/hwui/FontRenderer.cpp
index 7e99a5f..00e7870 100644
--- a/libs/hwui/FontRenderer.cpp
+++ b/libs/hwui/FontRenderer.cpp
@@ -353,7 +353,7 @@
                 memset(dstR += dstStride, 0, borderSize); // trailing border column
             }
             // write trailing border line
-            memset(dstL, 0, rowSize + 2 * borderSize);
+            memset(dstL += dstStride, 0, rowSize + 2 * borderSize);
             break;
         }
         case SkMask::kBW_Format: {