Various improvements to CodecSrc testing in dm

dm/DMSrcSink.h

Index: dm/DMSrcSink.h
diff --git a/dm/DMSrcSink.h b/dm/DMSrcSink.h
index 82a07258a8d785ac3e821e5568f4b55eec0d8581..da2dd46d59749e82b37d53dea993496f54d73130 100644
--- a/dm/DMSrcSink.h
+++ b/dm/DMSrcSink.h
@@ -102,7 +102,8 @@ private:
 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
@@ -113,17 +114,21 @@ public:
         kIndex8_Always_DstColorType,
         kGrayscale_Always_DstColorType,
     };
-    CodecSrc(Path, Mode, DstColorType, float);
+    CodecSrc(Path, Mode, DstColorType, float, SkString*);
 
     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;
+    // Because we are not using a literal, we must keep the
+    // name of the output directory as a field, so it remains
+    // in live memory until it is used.
+    SkAutoTDelete<SkString> fFolder;
 };