Make DMSrcSink fail fatally when decodeRegion() fails for BRDSrcs

tools/SkBitmapRegionDecoderInterface.cpp

 /*
  * Copyright 2015 Google Inc.
  *
  * Use of this source code is governed by a BSD-style license that can be
  * found in the LICENSE file.
  */
 
 #include "SkBitmapRegionCanvas.h"
 #include "SkBitmapRegionCodec.h"
 #include "SkBitmapRegionDecoderInterface.h"
@@ skipping 26 matching lines @@
                 return nullptr;
             }
             return new SkBitmapRegionSampler(decoder, width, height);
         }
         case kCanvas_Strategy: {
             SkAutoTDelete<SkCodec> codec(SkCodec::NewFromStream(streamDeleter.detach()));
             if (nullptr == codec) {
                 SkCodecPrintf("Error: Failed to create decoder.\n");
                 return nullptr;
             }
+
+            if (SkEncodedFormat::kWEBP_SkEncodedFormat == codec->getEncodedFormat()) {
+                // FIXME: Support webp using a special case.  Webp does not support
+                //        scanline decoding.
+                return nullptr;
+            }
+
             switch (codec->getScanlineOrder()) {
                 case SkCodec::kTopDown_SkScanlineOrder:
                 case SkCodec::kNone_SkScanlineOrder:
                     break;
                 default:
                     SkCodecPrintf("Error: Scanline ordering not supported.\n");
                     return nullptr;
             }
             return new SkBitmapRegionCanvas(codec.detach());
         }
         case kAndroidCodec_Strategy: {
             SkAutoTDelete<SkAndroidCodec> codec =
                     SkAndroidCodec::NewFromStream(streamDeleter.detach());
             if (NULL == codec) {
                 SkCodecPrintf("Error: Failed to create codec.\n");
                 return NULL;
             }
             return new SkBitmapRegionCodec(codec.detach());
         }
         default:
             SkASSERT(false);
             return nullptr;
     }
 }