don't rely on canvas->readPixels

Bug: skia:3216
Change-Id: I01a8d0083c79c0fe71fbc4d8cfdde4fa6e48b636
Reviewed-on: https://skia-review.googlesource.com/25741
Commit-Queue: Mike Reed <reed@google.com>
Reviewed-by: Brian Salomon <bsalomon@google.com>
diff --git a/tests/ApplyGammaTest.cpp b/tests/ApplyGammaTest.cpp
index 83b5968..f2049e7 100644
--- a/tests/ApplyGammaTest.cpp
+++ b/tests/ApplyGammaTest.cpp
@@ -129,7 +129,7 @@
         dstCanvas->flush();
 
         sk_memset32(read.get(), 0, kW * kH);
-        if (!dstCanvas->readPixels(ii, read.get(), kRowBytes, 0, 0)) {
+        if (!dst->readPixels(ii, read.get(), kRowBytes, 0, 0)) {
             ERRORF(reporter, "Error calling readPixels");
             continue;
         }