Add decodeYUV8Planes to SkImageDecoder_empty

BUG=skia:4562

Review URL: https://codereview.chromium.org/1456603002
diff --git a/src/ports/SkImageDecoder_empty.cpp b/src/ports/SkImageDecoder_empty.cpp
index 851e23d..624457b 100644
--- a/src/ports/SkImageDecoder_empty.cpp
+++ b/src/ports/SkImageDecoder_empty.cpp
@@ -43,6 +43,11 @@
     return false;
 }
 
+bool SkImageDecoder::decodeYUV8Planes(SkStream*, SkISize[3], void*[3],
+                                      size_t[3], SkYUVColorSpace*) {
+    return false;
+}
+
 SkImageDecoder::Format SkImageDecoder::getFormat() const {
     return kUnknown_Format;
 }