Add query to test our cached convexity

Sometimes our cache of convexity is wrong -- still trying to figure out
what do do about that.

Change-Id: Ie36292b87c4d07fc18643cc91f93be00c577b2ca
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/355616
Reviewed-by: Brian Salomon <bsalomon@google.com>
Commit-Queue: Mike Reed <reed@google.com>

include/core/SkPath.h

@@ -1850,17 +1850,15 @@ private:
     /** Returns the comvexity type, computing if needed. Never returns kUnknown.
         @return  path's convexity type (convex or concave)
     */
-    SkPathConvexity getConvexity() const {
-        SkPathConvexity convexity = this->getConvexityOrUnknown();
-        if (convexity == SkPathConvexity::kUnknown) {
-            convexity = this->computeConvexity();
-        }
-        SkASSERT(convexity != SkPathConvexity::kUnknown);
-        return convexity;
-    }
+    SkPathConvexity getConvexity() const;
+
     SkPathConvexity getConvexityOrUnknown() const {
         return (SkPathConvexity)fConvexity.load(std::memory_order_relaxed);
     }
+
+    // Compares the cached value with a freshly computed one (computeConvexity())
+    bool isConvexityAccurate() const;
+
     /** Stores a convexity type for this path. This is what will be returned if
      *  getConvexityOrUnknown() is called. If you pass kUnknown, then if getContexityType()
      *  is called, the real convexity will be computed.

src/core/SkPath.cpp

@@ -580,6 +580,29 @@ SkPathFirstDirection SkPath::getFirstDirection() const {
     return (SkPathFirstDirection)fFirstDirection.load(std::memory_order_relaxed);
 }
 
+bool SkPath::isConvexityAccurate() const {
+    SkPathConvexity convexity = this->getConvexityOrUnknown();
+    if (convexity != SkPathConvexity::kUnknown) {
+        auto conv = this->computeConvexity();
+        if (conv != convexity) {
+            SkASSERT(false);
+            return false;
+        }
+    }
+    return true;
+}
+
+SkPathConvexity SkPath::getConvexity() const {
+// Enable once we fix all the bugs
+//    SkDEBUGCODE(this->isConvexityAccurate());
+    SkPathConvexity convexity = this->getConvexityOrUnknown();
+    if (convexity == SkPathConvexity::kUnknown) {
+        convexity = this->computeConvexity();
+    }
+    SkASSERT(convexity != SkPathConvexity::kUnknown);
+    return convexity;
+}
+
 //////////////////////////////////////////////////////////////////////////////
 //  Construction methods