Add subsetting to SkScaledCodec

dm/DMSrcSink.cpp

Index: dm/DMSrcSink.cpp
diff --git a/dm/DMSrcSink.cpp b/dm/DMSrcSink.cpp
index 88371a8e28fdf68e1e0e5e041588a3a475e4adc1..23f42af133942d29608819584c32c2f344f38401 100644
--- a/dm/DMSrcSink.cpp
+++ b/dm/DMSrcSink.cpp
@@ -86,7 +86,7 @@ static SkBitmapRegionDecoderInterface* create_brd(Path path,
         SkBitmapRegionDecoderInterface::Strategy strategy) {
     SkAutoTUnref<SkData> encoded(SkData::NewFromFileName(path.c_str()));
     if (!encoded) {
-        return NULL;
+        return nullptr;
     }
     return SkBitmapRegionDecoderInterface::CreateBitmapRegionDecoder(new SkMemoryStream(encoded),
             strategy);
@@ -114,6 +114,10 @@ Error BRDSrc::draw(SkCanvas* canvas) const {
         return Error::Nonfatal(SkStringPrintf("Could not create brd for %s.", fPath.c_str()));
     }
 
+    if (!brd->conversionSupported(colorType)) {
+        return Error::Nonfatal("Cannot convert to color type.\n");
+    }
+
     const uint32_t width = brd->width();
     const uint32_t height = brd->height();
     // Visually inspecting very small output images is not necessary.
@@ -244,7 +248,7 @@ Error CodecSrc::draw(SkCanvas* canvas) const {
     if (!encoded) {
         return SkStringPrintf("Couldn't read %s.", fPath.c_str());
     }
-    SkAutoTDelete<SkCodec> codec(NULL);
+    SkAutoTDelete<SkCodec> codec(nullptr);
     if (kScaledCodec_Mode == fMode) {
         codec.reset(SkScaledCodec::NewFromData(encoded));
         // TODO (msarett): This should fall through to a fatal error once we support scaled