Revive quad approximation stroker

src/core/SkStrokeRec.cpp

 /*
  * Copyright 2012 Google Inc.
  *
  * Use of this source code is governed by a BSD-style license that can be
  * found in the LICENSE file.
  */
 
 #include "SkStrokeRec.h"
 #include "SkPaintDefaults.h"
 
@@ skipping 82 matching lines @@
         // hairline+fill == fill
         this->setFillStyle();
     } else {
         fWidth = width;
         fStrokeAndFill = strokeAndFill;
     }
 }
 
 #include "SkStroke.h"
 
+#if defined SK_QUAD_STROKE_APPROXIMATION && defined SK_DEBUG  
+    // enables tweaking these values at runtime from SampleApp
+    bool gDebugStrokerErrorSet = false;
+    SkScalar gDebugStrokerError;
+#endif
+
 bool SkStrokeRec::applyToPath(SkPath* dst, const SkPath& src) const {
     if (fWidth <= 0) {  // hairline or fill
         return false;
     }
 
     SkStroke stroker;
     stroker.setCap(fCap);
     stroker.setJoin(fJoin);
     stroker.setMiterLimit(fMiterLimit);
     stroker.setWidth(fWidth);
     stroker.setDoFill(fStrokeAndFill);
+#if defined SK_QUAD_STROKE_APPROXIMATION && defined SK_DEBUG
+    stroker.setResScale(gDebugStrokerErrorSet ? gDebugStrokerError : fResScale);
+#else
     stroker.setResScale(fResScale);
-#if QUAD_STROKE_APPROXIMATION
-    stroker.setError(1);
 #endif
     stroker.strokePath(src, dst);
     return true;
 }
 
 void SkStrokeRec::applyToPaint(SkPaint* paint) const {
     if (fWidth < 0) {  // fill
         paint->setStyle(SkPaint::kFill_Style);
         return;
     }
 
     paint->setStyle(fStrokeAndFill ? SkPaint::kStrokeAndFill_Style : SkPaint::kStroke_Style);
     paint->setStrokeWidth(fWidth);
     paint->setStrokeMiter(fMiterLimit);
     paint->setStrokeCap(fCap);
     paint->setStrokeJoin(fJoin);
 }