make info real in SkPixelRef, and add bitmap::asImageInfo

src/images/SkDecodingImageGenerator.cpp

Index: src/images/SkDecodingImageGenerator.cpp
diff --git a/src/images/SkDecodingImageGenerator.cpp b/src/images/SkDecodingImageGenerator.cpp
index 2b804441417938042168d4ddce2b65232faceb30..e49f9a4f24350575fa8bbef966569345d5b4a497 100644
--- a/src/images/SkDecodingImageGenerator.cpp
+++ b/src/images/SkDecodingImageGenerator.cpp
@@ -119,11 +119,9 @@ bool SkDecodingImageGenerator::getInfo(SkImageInfo* info) {
     if (bitmap.config() == SkBitmap::kNo_Config) {
         return false;
     }
-    if (!SkBitmapToImageInfo(bitmap, &fInfo)) {
+    if (!bitmap.asImageInfo(&fInfo)) {
         // We can't use bitmap.config() as is.
-        // Must be kARGB_4444_Config.
         if (!bitmap.canCopyTo(SkBitmap::kARGB_8888_Config)) {
-            // kARGB_4444_Config can copy to kARGB_8888.
             SkDEBUGFAIL("!bitmap->canCopyTo(SkBitmap::kARGB_8888_Config)");
             return false;
         }