Hack together MSAN build.

src/images/SkImageDecoder_libjpeg.cpp

Index: src/images/SkImageDecoder_libjpeg.cpp
diff --git a/src/images/SkImageDecoder_libjpeg.cpp b/src/images/SkImageDecoder_libjpeg.cpp
index 6a032fdb9626703ffe3d8a669b497759339d6bd0..6a3ae87b6a113da85e3291d7a91e3526ffde5140 100644
--- a/src/images/SkImageDecoder_libjpeg.cpp
+++ b/src/images/SkImageDecoder_libjpeg.cpp
@@ -11,6 +11,7 @@
 #include "SkJpegUtility.h"
 #include "SkColorPriv.h"
 #include "SkDither.h"
+#include "SkMSAN.h"
 #include "SkScaledBitmapSampler.h"
 #include "SkStream.h"
 #include "SkTemplates.h"
@@ -524,6 +525,9 @@ SkImageDecoder::Result SkJPEGImageDecoder::onDecode(SkStream* stream, SkBitmap*
             convert_CMYK_to_RGB(srcRow, cinfo.output_width);
         }
 
+        sk_msan_mark_initialized(srcRow, srcRow + cinfo.output_width * srcBytesPerPixel,
+                                 "skbug.com/4550");
+
         sampler.next(srcRow);
         if (bm->height() - 1 == y) {
             // we're done