use some helper Make functions to initialize SkImageInfo

src/core/SkScaledImageCache.cpp

Index: src/core/SkScaledImageCache.cpp
diff --git a/src/core/SkScaledImageCache.cpp b/src/core/SkScaledImageCache.cpp
index fc3148bdd8807a31f0660c7f45b36e78bdcd1f41..d87597315f034121d0e7e6effe1a16f0732a3a1f 100644
--- a/src/core/SkScaledImageCache.cpp
+++ b/src/core/SkScaledImageCache.cpp
@@ -293,13 +293,8 @@ bool SkScaledImageCacheDiscardableAllocator::allocPixelRef(SkBitmap* bitmap,
         return false;
     }
 
-    SkImageInfo info = {
-        bitmap->width(),
-        bitmap->height(),
-        kPMColor_SkColorType,
-        bitmap->alphaType()
-    };
-
+    SkImageInfo info = SkImageInfo::MakeN32(bitmap->width(), bitmap->height(),
+                                            bitmap->alphaType());
     bitmap->setPixelRef(SkNEW_ARGS(SkOneShotDiscardablePixelRef,
                                    (info, dm, bitmap->rowBytes())))->unref();
     bitmap->lockPixels();