Add CodecZeroInit test to DMSrcSink

dm/DMSrcSink.cpp

Index: dm/DMSrcSink.cpp
diff --git a/dm/DMSrcSink.cpp b/dm/DMSrcSink.cpp
index c9bdcf6706771a6b253756ed7827d8d354eb3c56..42104b3e611bda145558f793c602b3f810f89ad1 100644
--- a/dm/DMSrcSink.cpp
+++ b/dm/DMSrcSink.cpp
@@ -321,9 +321,14 @@ Error CodecSrc::draw(SkCanvas* canvas) const {
                               decodeInfo.width(), decodeInfo.height());
     }
 
+    SkCodec::Options options;
     switch (fMode) {
+        case kCodecZeroInit_Mode:
+            options.fZeroInitialized = SkCodec::kYes_ZeroInitialized;
+            bitmap.eraseColor(0);

[scroggo, 2016/01/12 22:27:46]

This won't work for index8 bitmaps. Instead, we can use an allocator which calls
calloc.

[mtklein, 2016/01/12 22:51:22]

e.g. SkMallocPixelRef::NewZeroed() / SkMallocPixelRef::ZeroedPRFactory.

[msarett, 2016/01/13 14:58:16]

Done.

+            // Intentional fall through.
         case kCodec_Mode: {
-            switch (codec->getPixels(decodeInfo, bitmap.getPixels(), bitmap.rowBytes(), nullptr,
+            switch (codec->getPixels(decodeInfo, bitmap.getPixels(), bitmap.rowBytes(), &options,
                     colorPtr, colorCountPtr)) {
                 case SkCodec::kSuccess:
                     // We consider incomplete to be valid, since we should still decode what is