fix bugs found by computing flat clips in 800K skps

src/pathops/SkPathOpsLine.cpp

Index: src/pathops/SkPathOpsLine.cpp
diff --git a/src/pathops/SkPathOpsLine.cpp b/src/pathops/SkPathOpsLine.cpp
index 7587fda69ab57d0ca112b1a0dfc631103fcfbfbc..622961911a4dbc4de25dccad58825872498cb9e6 100644
--- a/src/pathops/SkPathOpsLine.cpp
+++ b/src/pathops/SkPathOpsLine.cpp
@@ -63,7 +63,7 @@ double SkDLine::exactPoint(const SkDPoint& xy) const {
     return -1;
 }
 
-double SkDLine::nearPoint(const SkDPoint& xy) const {
+double SkDLine::nearPoint(const SkDPoint& xy, bool* unequal) const {
     if (!AlmostBetweenUlps(fPts[0].fX, xy.fX, fPts[1].fX)
             || !AlmostBetweenUlps(fPts[0].fY, xy.fY, fPts[1].fY)) {
         return -1;
@@ -86,6 +86,9 @@ double SkDLine::nearPoint(const SkDPoint& xy) const {
     if (!AlmostEqualUlps(largest, largest + dist)) { // is the dist within ULPS tolerance?
         return -1;
     }
+    if (unequal) {
+        *unequal = (float) largest != (float) (largest + dist);
+    }
     t = SkPinT(t);
     SkASSERT(between(0, t, 1));
     return t;