use some helper Make functions to initialize SkImageInfo

BUG=
R=halcanary@google.com, scroggo@google.com

Author: reed@google.com

Review URL: https://codereview.chromium.org/137993012

git-svn-id: http://skia.googlecode.com/svn/trunk@13081 2bbb7eff-a529-9590-31e7-b0007b416f81
diff --git a/tests/PixelRefTest.cpp b/tests/PixelRefTest.cpp
index 3c735c6..d7fe9f4 100644
--- a/tests/PixelRefTest.cpp
+++ b/tests/PixelRefTest.cpp
@@ -50,7 +50,7 @@
 }  // namespace
 
 DEF_TEST(PixelRef_GenIDChange, r) {
-    SkImageInfo info = { 10, 10, kPMColor_SkColorType, kPremul_SkAlphaType };
+    SkImageInfo info = SkImageInfo::MakeN32Premul(10, 10);
 
     SkAutoTUnref<SkPixelRef> pixelRef(SkMallocPixelRef::NewAllocate(info, 0, NULL));