Revert of Change mapRectScaleTranslate to pass args/ret by value (patchset #2 id:20001 of https://codereview.chromium.org/2138943002/ )

Reason for revert:
Build-Ubuntu-GCC-Arm7-Release-Android fails.

Original issue's description:
> Change mapRectScaleTranslate to pass args/ret by value
>
> This reverts commit 6092b6e0e57be20d2e1ad079c0af133d2f67bfd3.
>
> BUG=skia:
> GOLD_TRYBOT_URL= https://gold.skia.org/search?issue=2138943002
>
> Committed: https://skia.googlesource.com/skia/+/1bd13ca922d6448d595064faee486eaf3fa56e56

TBR=mtklein@google.com,msarett@google.com,reed@google.com
# Skipping CQ checks because original CL landed less than 1 days ago.
NOPRESUBMIT=true
NOTREECHECKS=true
NOTRY=true
BUG=skia:

Review-Url: https://codereview.chromium.org/2234843002
diff --git a/tests/MatrixTest.cpp b/tests/MatrixTest.cpp
index 6cba604..414aab2 100644
--- a/tests/MatrixTest.cpp
+++ b/tests/MatrixTest.cpp
@@ -984,7 +984,7 @@
         mat.mapPoints((SkPoint*)&dst[0].fLeft, (SkPoint*)&src.fLeft, 2);
         dst[0].sort();
         mat.mapRect(&dst[1], src);
-        dst[2] = mat.mapRectScaleTranslate(src);
+        mat.mapRectScaleTranslate(&dst[2], src);
 
         REPORTER_ASSERT(r, dst[0] == dst[1]);
         REPORTER_ASSERT(r, dst[0] == dst[2]);