Fill incomplete images in SkCodec parent class

src/codec/SkWebpCodec.cpp

Index: src/codec/SkWebpCodec.cpp
diff --git a/src/codec/SkWebpCodec.cpp b/src/codec/SkWebpCodec.cpp
index ccffda9276857e9549cd9fb1263577b3a9c59d68..3e6d11feda2c101504cf68b1927dee4805b7417b 100644
--- a/src/codec/SkWebpCodec.cpp
+++ b/src/codec/SkWebpCodec.cpp
@@ -158,7 +158,8 @@ bool SkWebpCodec::onGetValidSubset(SkIRect* desiredSubset) const {
 }
 
 SkCodec::Result SkWebpCodec::onGetPixels(const SkImageInfo& dstInfo, void* dst, size_t rowBytes,
-                                         const Options& options, SkPMColor*, int*) {
+                                         const Options& options, SkPMColor*, int*,
+                                         int* rowsDecoded) {
     if (!webp_conversion_possible(dstInfo, this->getInfo())) {
         return kInvalidConversion;
     }
@@ -216,6 +217,7 @@ SkCodec::Result SkWebpCodec::onGetPixels(const SkImageInfo& dstInfo, void* dst,
         config.options.scaled_width = dstDimensions.width();
         config.options.scaled_height = dstDimensions.height();
     }
+    fDstWidth = dstDimensions.width();
 
     config.output.colorspace = webp_decode_mode(dstInfo.colorType(),
             dstInfo.alphaType() == kPremul_SkAlphaType);
@@ -234,10 +236,8 @@ SkCodec::Result SkWebpCodec::onGetPixels(const SkImageInfo& dstInfo, void* dst,
     while (true) {
         const size_t bytesRead = stream()->read(buffer, BUFFER_SIZE);
         if (0 == bytesRead) {
-            // FIXME: Maybe this is an incomplete image? How to decide? Based
-            // on the number of rows decoded? We can know the number of rows
-            // decoded using WebPIDecGetRGB.
-            return kInvalidInput;
+            WebPIDecGetRGB(idec, rowsDecoded, NULL, NULL, NULL);
+            return kIncompleteInput;
         }
 
         switch (WebPIAppend(idec, buffer, bytesRead)) {
@@ -253,4 +253,38 @@ SkCodec::Result SkWebpCodec::onGetPixels(const SkImageInfo& dstInfo, void* dst,
 }
 
 SkWebpCodec::SkWebpCodec(const SkImageInfo& info, SkStream* stream)
-    : INHERITED(info, stream) {}
+    : INHERITED(info, stream)
+    , fDstWidth(info.width())
+{}
+
+class SkWebpSampler : public SkSampler {
+public:
+    SkWebpSampler(SkWebpCodec* codec)
+        : fCodec(codec)
+    {
+        SkASSERT(fCodec);
+    }
+
+private:
+    // We not support sampling of webps.  Webps support arbitrary native scaling.
+    int onSetSampleX(int sampleX) {
+        SkASSERT(false);
+        return fCodec->fDstWidth;
+    }
+
+
+    int onGetScaledWidth() override {
+        return fCodec->fDstWidth;
+    }
+
+    // Unowned pointer. fCodec will delete this class in its destructor.
+    SkWebpCodec* fCodec;
+};
+
+SkSampler* SkWebpCodec::getSampler() {
+    if (!fSampler) {
+        fSampler.reset(new SkWebpSampler(this));
+    }
+
+    return fSampler;
+}