shape ops work in progress
add quartic solution for intersecting quadratics

git-svn-id: http://skia.googlecode.com/svn/trunk@5541 2bbb7eff-a529-9590-31e7-b0007b416f81
diff --git a/experimental/Intersection/QuadraticUtilities.cpp b/experimental/Intersection/QuadraticUtilities.cpp
index 8971fca..95be90a 100644
--- a/experimental/Intersection/QuadraticUtilities.cpp
+++ b/experimental/Intersection/QuadraticUtilities.cpp
@@ -28,8 +28,11 @@
 int quadraticRoots(double A, double B, double C, double t[2]) {
     B *= 2;
     double square = B * B - 4 * A * C;
-    if (square < 0) {
-        return 0;
+    if (approximately_negative(square)) {
+        if (!approximately_positive(square)) {
+            return 0;
+        }
+        square = 0;
     }
     double squareRt = sqrt(square);
     double Q = (B + (B < 0 ? -squareRt : squareRt)) / -2;