use some helper Make functions to initialize SkImageInfo

gm/srcmode.cpp

Index: gm/srcmode.cpp
diff --git a/gm/srcmode.cpp b/gm/srcmode.cpp
index 666a36bb040e2e300e61df59c03a3024dbbb1ddc..6aa236f3f4321c19fafb15d7d720f3234d46a6ed 100644
--- a/gm/srcmode.cpp
+++ b/gm/srcmode.cpp
@@ -117,12 +117,7 @@ protected:
 
     static SkSurface* compat_surface(SkCanvas* canvas, const SkISize& size,
                                      bool skipGPU) {
-        SkImageInfo info = {
-            size.width(),
-            size.height(),
-            kPMColor_SkColorType,
-            kPremul_SkAlphaType
-        };
+        SkImageInfo info = SkImageInfo::MakeN32Premul(size);
 #if SK_SUPPORT_GPU
         SkBaseDevice* dev = canvas->getDevice();
         if (!skipGPU && dev->accessRenderTarget()) {