Fix issue 3620...

webkit/port/platform/graphics/PathSkia.cpp

 // Copyright (c) 2008, Google Inc.
 // All rights reserved.
 // 
 // Redistribution and use in source and binary forms, with or without
 // modification, are permitted provided that the following conditions are
 // met:
 // 
 //     * Redistributions of source code must retain the above copyright
 // notice, this list of conditions and the following disclaimer.
 //     * Redistributions in binary form must reproduce the above
@@ skipping 125 matching lines @@
     oval.set(cx - radius, cy - radius, cx + radius, cy + radius);
     
     float sweep = ea - sa;
     // check for a circle
     if (sweep >= 2*gPI || sweep <= -2*gPI) {
         m_path->addOval(oval);
     } else {
         SkScalar startDegrees = WebCoreFloatToSkScalar(sa * 180 / gPI);
         SkScalar sweepDegrees = WebCoreFloatToSkScalar(sweep * 180 / gPI);
 
+        // Counterclockwise arcs should be drawn with negative sweeps, while
+        // clockwise arcs should be drawn with positive sweeps. Check to see
+        // if the situation is reversed and correct it by adding or subtracting
+        // a full circle
         if (anticlockwise && sweepDegrees > 0) {
             sweepDegrees -= SkIntToScalar(360);
         } else if (!anticlockwise && sweepDegrees < 0) {
-            sweepDegrees = SkIntToScalar(360) - sweepDegrees;
+            sweepDegrees += SkIntToScalar(360);
         }
 
 //        SkDebugf("addArc sa=%g ea=%g cw=%d start=%g sweep=%g\n", sa, ea, clockwise,
 //                 SkScalarToFloat(startDegrees), SkScalarToFloat(sweepDegrees));
 
         m_path->arcTo(oval, startDegrees, sweepDegrees, false);
     }
 }
 
 void Path::addRect(const FloatRect& rect)
@@ skipping 113 matching lines @@
     if (numPoints) {
         ASSERT(numPoints==1);
         m_path->getLastPt(pts);
         result += String::format("M%.2f,%.2f ", pts[0].fX, pts[0].fY);
     }
 
     return result.stripWhiteSpace();
 }
 
 } // namespace WebCore