Implement onSkipScanlines() for bmp and wbmp

include/codec/SkCodec.h

 /*
  * Copyright 2015 Google Inc.
  *
  * Use of this source code is governed by a BSD-style license that can be
  * found in the LICENSE file.
  */
 
 #ifndef SkCodec_DEFINED
 #define SkCodec_DEFINED
 
@@ skipping 639 matching lines @@
     bool dimensionsSupported(const SkISize& dim) {
         return dim == fSrcInfo.dimensions() || this->onDimensionsSupported(dim);
     }
 
     // Methods for scanline decoding.
     virtual SkCodec::Result onStartScanlineDecode(const SkImageInfo& /*dstInfo*/,
             const SkCodec::Options& /*options*/, SkPMColor* /*ctable*/, int* /*ctableCount*/) {
         return kUnimplemented;
     }
 
-    // Naive default version just calls onGetScanlines on temp memory.
-    virtual bool onSkipScanlines(int countLines) {
-        // FIXME (msarett): Make this a pure virtual and always override this.
-        SkAutoMalloc storage(fDstInfo.minRowBytes());
-
-        // Note that we pass 0 to rowBytes so we continue to use the same memory.
-        // Also note that while getScanlines checks that rowBytes is big enough,
-        // onGetScanlines bypasses that check.
-        // Calling the virtual method also means we do not double count
-        // countLines.
-        return countLines == this->onGetScanlines(storage.get(), countLines, 0);
-    }
+    virtual bool onSkipScanlines(int /*countLines*/) { return false; }
 
     virtual int onGetScanlines(void* /*dst*/, int /*countLines*/, size_t /*rowBytes*/) { return 0; }
 
     /**
      * On an incomplete decode, getPixels() and getScanlines() will call this function
      * to fill any uinitialized memory.
      *
      * @param dstInfo        Contains the destination color type
      *                       Contains the destination alpha type
      *                       Contains the destination width
@@ skipping 14 matching lines @@
      *  not affect ownership.
      *
      *  Only valid during scanline decoding.
      */
     virtual SkSampler* getSampler(bool /*createIfNecessary*/) { return nullptr; }
 
     friend class SkSampledCodec;
     friend class SkIcoCodec;
 };
 #endif // SkCodec_DEFINED