Add scaled subset API to SkCodec

src/codec/SkSwizzler.cpp

Index: src/codec/SkSwizzler.cpp
diff --git a/src/codec/SkSwizzler.cpp b/src/codec/SkSwizzler.cpp
index 95ed1d7b962f58f96836a66be01389853591105b..9c7df4350dd1ccd62e4d369cc3c132288b8a09cd 100644
--- a/src/codec/SkSwizzler.cpp
+++ b/src/codec/SkSwizzler.cpp
@@ -710,9 +710,6 @@ int SkSwizzler::onSetSampleX(int sampleX) {
     fSampleX = sampleX;
     fX0 = get_start_coord(sampleX) + fSrcOffset;
     fDstWidth = get_scaled_dimension(fSrcWidth, sampleX);
-

[msarett, 2015/10/12 18:33:29]

I missed this in an earlier CL, but this check is no longer valid.

We may want a ten pixel subset that starts twenty pixels from the left edge of
the image.

This is completely valid, but in this case fX0 = 20 and fSrcWidth = 10.

[scroggo, 2015/10/12 20:47:07]

Wait, does this belong in crrev.com/1390213002? I would prefer it go in with
that one (or by itself) than here.

-    // check that fX0 is less than original width
-    SkASSERT(fX0 >= 0 && fX0 < fSrcWidth);
     return fDstWidth;
 }