Add subsetting to SkScaledCodec

src/codec/SkCodec_libpng.cpp

Index: src/codec/SkCodec_libpng.cpp
diff --git a/src/codec/SkCodec_libpng.cpp b/src/codec/SkCodec_libpng.cpp
index 0db425c3544d73e9fa986643ac09c9f90e7d9c47..4bde36a43191f0300e03c22fb5a7cb515ab97fd6 100644
--- a/src/codec/SkCodec_libpng.cpp
+++ b/src/codec/SkCodec_libpng.cpp
@@ -394,7 +394,9 @@ void SkPngCodec::destroyReadStruct() {
 SkCodec::Result SkPngCodec::initializeSwizzler(const SkImageInfo& requestedInfo,
                                                const Options& options,
                                                SkPMColor ctable[],
-                                               int* ctableCount) {
+                                               int* ctableCount,
+                                               int subsetLeft,
+                                               int subsetWidth) {
     // FIXME: Could we use the return value of setjmp to specify the type of
     // error?
     if (setjmp(png_jmpbuf(fPng_ptr))) {
@@ -436,7 +438,7 @@ SkCodec::Result SkPngCodec::initializeSwizzler(const SkImageInfo& requestedInfo,
     // Create the swizzler.  SkPngCodec retains ownership of the color table.
     const SkPMColor* colors = get_color_ptr(fColorTable.get());
     fSwizzler.reset(SkSwizzler::CreateSwizzler(fSrcConfig, colors, requestedInfo,
-                                               options.fZeroInitialized));
+                    options.fZeroInitialized, subsetLeft, subsetWidth));
     if (!fSwizzler) {
         // FIXME: CreateSwizzler could fail for another reason.
         return kUnimplemented;
@@ -477,8 +479,8 @@ SkCodec::Result SkPngCodec::onGetPixels(const SkImageInfo& requestedInfo, void*
     }
 
     // Note that ctable and ctableCount may be modified if there is a color table
-    const Result result = this->initializeSwizzler(requestedInfo, options,
-                                                   ctable, ctableCount);
+    const Result result = this->initializeSwizzler(requestedInfo, options, ctable, ctableCount, 0,
+            requestedInfo.width());
     if (result != kSuccess) {
         return result;
     }
@@ -611,13 +613,13 @@ public:
     {}
 
     Result onStartScanlineDecode(const SkImageInfo& dstInfo, const Options& options,
-            SkPMColor ctable[], int* ctableCount) override {
+            SkPMColor ctable[], int* ctableCount, int subsetLeft, int subsetWidth) override {
         if (!conversion_possible(dstInfo, this->getInfo())) {
             return kInvalidConversion;
         }
 
         const Result result = this->initializeSwizzler(dstInfo, options, ctable,
-                                                       ctableCount);
+                                                       ctableCount, subsetLeft, subsetWidth);
         if (result != kSuccess) {
             return result;
         }
@@ -698,15 +700,14 @@ public:
     }
 
     Result onStartScanlineDecode(const SkImageInfo& dstInfo, const Options& options,
-            SkPMColor ctable[], int* ctableCount) override
-    {
+            SkPMColor ctable[], int* ctableCount, int subsetLeft, int subsetWidth) override {
         if (!conversion_possible(dstInfo, this->getInfo())) {
             return kInvalidConversion;    
         }
 
-        const SkCodec::Result result = this->initializeSwizzler(dstInfo, options, ctable,
-                                                                ctableCount);
-        if (result != SkCodec::kSuccess) {
+        const Result result = this->initializeSwizzler(dstInfo, options, ctable,
+                                                       ctableCount, subsetLeft, subsetWidth);
+        if (result != kSuccess) {
             return result;
         }