Handle negative scale in SkDropShadowImageFilter::onFilterNodeBounds.

src/effects/SkDropShadowImageFilter.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 "SkDropShadowImageFilter.h"
 
 #include "SkBlurImageFilter.h"
@@ skipping 121 matching lines @@
                                                     MapDirection direction) const {
     SkVector offsetVec = SkVector::Make(fDx, fDy);
     if (kReverse_MapDirection == direction) {
         offsetVec.negate();
     }
     ctm.mapVectors(&offsetVec, 1);
     SkIRect dst = src.makeOffset(SkScalarCeilToInt(offsetVec.x()),
                                  SkScalarCeilToInt(offsetVec.y()));
     SkVector sigma = SkVector::Make(fSigmaX, fSigmaY);
     ctm.mapVectors(&sigma, 1);
-    dst.outset(SkScalarCeilToInt(SkScalarMul(sigma.x(), SkIntToScalar(3))),
-                SkScalarCeilToInt(SkScalarMul(sigma.y(), SkIntToScalar(3))));
+    dst.outset(
+        SkScalarCeilToInt(SkScalarAbs(SkScalarMul(sigma.x(), SkIntToScalar(3)))),

[Stephen White, 2016/07/12 16:25:23]

There's probably a similar bug in SkDSIF::computeFastBounds().

+        SkScalarCeilToInt(SkScalarAbs(SkScalarMul(sigma.y(), SkIntToScalar(3)))));
     if (fShadowMode == kDrawShadowAndForeground_ShadowMode) {
         dst.join(src);
     }
     return dst;
 }
 
 #ifndef SK_IGNORE_TO_STRING
 void SkDropShadowImageFilter::toString(SkString* str) const {
     str->appendf("SkDropShadowImageFilter: (");
 
     str->appendf("dX: %f ", fDx);
     str->appendf("dY: %f ", fDy);
     str->appendf("sigmaX: %f ", fSigmaX);
     str->appendf("sigmaY: %f ", fSigmaY);
 
     str->append("Color: ");
     str->appendHex(fColor);
 
     static const char* gModeStrings[] = {
         "kDrawShadowAndForeground", "kDrawShadowOnly"
     };
 
     static_assert(kShadowModeCount == SK_ARRAY_COUNT(gModeStrings), "enum_mismatch");
 
     str->appendf(" mode: %s", gModeStrings[fShadowMode]);
 
     str->append(")");
 }
 #endif