Various improvements to CodecSrc testing in dm

dm/DMSrcSink.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 DMSrcSink_DEFINED
 #define DMSrcSink_DEFINED
 
 #include "DMGpuSupport.h"
 #include "SkBBHFactory.h"
 #include "SkBBoxHierarchy.h"
 #include "SkBitmap.h"
 #include "SkCanvas.h"
 #include "SkData.h"
 #include "SkGPipe.h"
 #include "SkPicture.h"
 #include "gm.h"
 
 namespace DM {
 
 // This is just convenience.  It lets you use either return "foo" or return SkStringPrintf(...).
 struct ImplicitString : public SkString {
     template <typename T>
     ImplicitString(const T& s) : SkString(s) {}
+    ImplicitString() : SkString("") {}
 };
 typedef ImplicitString Name;
 typedef ImplicitString Path;
 
 class Error {
 public:
     Error(const SkString& s) : fMsg(s), fFatal(!this->isEmpty()) {}
     Error(const char* s)     : fMsg(s), fFatal(!this->isEmpty()) {}
 
     Error(const Error&)            = default;
@@ skipping 58 matching lines @@
     Name name() const override;
     void modifyGrContextOptions(GrContextOptions* options) const override;
 
 private:
     skiagm::GMRegistry::Factory fFactory;
 };
 
 class CodecSrc : public Src {
 public:
     enum Mode {
-        kNormal_Mode,
+        kScaledCodec_Mode,
+        kCodec_Mode,
         kScanline_Mode,
         kScanline_Subset_Mode,
         kStripe_Mode, // Tests the skipping of scanlines
         kSubset_Mode, // For codecs that support subsets directly.
     };
     enum DstColorType {
         kGetFromCanvas_DstColorType,
         kIndex8_Always_DstColorType,
         kGrayscale_Always_DstColorType,
     };
     CodecSrc(Path, Mode, DstColorType, float);
 
     Error draw(SkCanvas*) const override;
     SkISize size() const override;
     Name name() const override;
     bool veto(SinkFlags) const override;
 private:
-    Path                   fPath;
-    Mode                   fMode;
-    DstColorType           fDstColorType;
-    float                  fScale;
+    Path                    fPath;
+    Mode                    fMode;
+    DstColorType            fDstColorType;
+    float                   fScale;
 };
 
 
 class ImageSrc : public Src {
 public:
     // divisor == 0 means decode the whole image
     // divisor > 0 means decode in subsets, dividing into a divisor x divisor grid.
     explicit ImageSrc(Path path, int divisor = 0);
 
     Error draw(SkCanvas*) const override;
@@ skipping 171 matching lines @@
 
 class ViaTwice : public Via {
 public:
     explicit ViaTwice(Sink* sink) : Via(sink) {}
     Error draw(const Src&, SkBitmap*, SkWStream*, SkString*) const override;
 };
 
 }  // namespace DM
 
 #endif//DMSrcSink_DEFINED