fix bugs found by computing flat clips in 800K skps

src/pathops/SkDQuadIntersection.cpp

 // Another approach is to start with the implicit form of one curve and solve
 // (seek implicit coefficients in QuadraticParameter.cpp
 // by substituting in the parametric form of the other.
 // The downside of this approach is that early rejects are difficult to come by.
 // http://planetmath.org/encyclopedia/GaloisTheoreticDerivationOfTheQuarticFormula.html#step
 
 #include "SkDQuadImplicit.h"
 #include "SkIntersections.h"
 #include "SkPathOpsLine.h"
 #include "SkQuarticRoot.h"
@@ skipping 404 matching lines @@
     }
     // see if either quad is really a line
     // FIXME: figure out why reduce step didn't find this earlier
     if (is_linear(q1, q2, this)) {
         return fUsed;
     }
     SkIntersections swapped;
     swapped.setMax(fMax);
     if (is_linear(q2, q1, &swapped)) {
         swapped.swapPts();
-        set(swapped);
+        *this = swapped;
         return fUsed;
     }
     SkIntersections copyI(*this);
     lookNearEnd(q1, q2, 0, *this, false, &copyI);
     lookNearEnd(q1, q2, 1, *this, false, &copyI);
     lookNearEnd(q2, q1, 0, *this, true, &copyI);
     lookNearEnd(q2, q1, 1, *this, true, &copyI);
     int innerEqual = 0;
     if (copyI.fUsed >= 2) {
         SkASSERT(copyI.fUsed <= 4);
@@ skipping 110 matching lines @@
         }
         if (lowestIndex < 0) {
             break;
         }
         insert(roots1Copy[lowestIndex], roots2Copy[closest[lowestIndex]],
                 pts1[lowestIndex]);
         closest[lowestIndex] = -1;
     } while (++used < r1Count);
     return fUsed;
 }