Fix bug in sampled decodes

src/codec/SkSampledCodec.cpp

Index: src/codec/SkSampledCodec.cpp
diff --git a/src/codec/SkSampledCodec.cpp b/src/codec/SkSampledCodec.cpp
index 5302149e1212ba6a14d34e6a29878c24fdfc1d3f..d5fbd0fa520615a4a750674ea792bb199b7bdfb9 100644
--- a/src/codec/SkSampledCodec.cpp
+++ b/src/codec/SkSampledCodec.cpp
@@ -215,11 +215,12 @@ SkCodec::Result SkSampledCodec::sampledDecode(const SkImageInfo& info, void* pix
                             dstHeight, y + 1);
                     return SkCodec::kIncompleteInput;
                 }
-                int linesToSkip = SkTMin(sampleY - 1, dstHeight - y - 1);

[msarett, 2015/11/05 17:57:19]

I think the intent here was to not skip past the end of the image.

However, dstHeight - y - 1 doesn't make any sense.  I think what we want is:
srcHeight - fCurrScanline

Or, even better, we can just not skip on the last iteration.

-                if (!fCodec->skipScanlines(linesToSkip)) {
-                    fCodec->fillIncompleteImage(info, pixels, rowBytes, options.fZeroInitialized,
-                            dstHeight, y + 1);
-                    return SkCodec::kIncompleteInput;
+                if (y < dstHeight - 1) {
+                    if (!fCodec->skipScanlines(sampleY - 1)) {
+                        fCodec->fillIncompleteImage(info, pixels, rowBytes,
+                                options.fZeroInitialized, dstHeight, y + 1);
+                        return SkCodec::kIncompleteInput;
+                    }
                 }
                 pixelPtr = SkTAddOffset<void>(pixelPtr, rowBytes);
             }