Do not attempt to scale webp.

dm/DM.cpp

 /*
  * Copyright 2013 Google Inc.
  *
  * Use of this source code is governed by a BSD-style license that can be
  * found in the LICENSE file.
  */
 
 #include "CrashHandler.h"
 #include "DMJsonWriter.h"
 #include "DMSrcSink.h"
@@ skipping 194 matching lines @@
         return;
     }
 
     // Choose scales for scaling tests.
     // TODO (msarett): Add more scaling tests as we implement more flexible scaling.
     // TODO (msarett): Implement scaling tests for SkImageDecoder in order to compare with these
     //                 tests.  SkImageDecoder supports downscales by integer factors.
     const float scales[] = { 0.125f, 0.25f, 0.375f, 0.5f, 0.625f, 0.750f, 0.875f, 1.0f };
 
     for (float scale : scales) {
+        if (scale != 1.0f && (path.endsWith(".webp") || path.endsWith(".WEBP"))) {
+            // FIXME: skbug.com/4038 Scaling webp seems to leave some pixels uninitialized/
+            // compute their colors based on uninitialized values.
+            continue;
+        }
         // Build additional test cases for images that decode natively to non-canvas types
         switch(codec->getInfo().colorType()) {
             case kGray_8_SkColorType:
                 push_src("image", "codec_kGray8", new CodecSrc(path, CodecSrc::kNormal_Mode,
                         CodecSrc::kGrayscale_Always_DstColorType, scale));
                 push_src("image", "scanline_kGray8", new CodecSrc(path, CodecSrc::kScanline_Mode,
                         CodecSrc::kGrayscale_Always_DstColorType, scale));
                 push_src("image", "scanline_subset_kGray8", new CodecSrc(path,
                         CodecSrc::kScanline_Subset_Mode, CodecSrc::kGrayscale_Always_DstColorType,
                         scale));
@@ skipping 596 matching lines @@
     }
     return 0;
 }
 
 #if !defined(SK_BUILD_FOR_IOS)
 int main(int argc, char** argv) {
     SkCommandLineFlags::Parse(argc, argv);
     return dm_main();
 }
 #endif