fix misc asserts and checks found by fuzzer

src/effects/SkDashPathEffect.cpp

 /*
  * Copyright 2006 The Android Open Source Project
  *
  * Use of this source code is governed by a BSD-style license that can be
  * found in the LICENSE file.
  */
 
 #include "SkDashPathEffect.h"
 
 #include "SkDashPathPriv.h"
@@ skipping 366 matching lines @@
     str->appendf("count: %d phase %.2f intervals: (", fCount, fPhase);
     for (int i = 0; i < fCount; ++i) {
         str->appendf("%.2f", fIntervals[i]);
         if (i < fCount-1) {
             str->appendf(", ");
         }
     }
     str->appendf("))");
 }
 #endif
+
+//////////////////////////////////////////////////////////////////////////////////////////////////
+
+SkPathEffect* SkDashPathEffect::Create(const SkScalar intervals[], int count, SkScalar phase) {
+    if ((count < 2) || !SkIsAlign2(count)) {
+        return nullptr;
+    }
+    for (int i = 0; i < count; i++) {
+        if (intervals[i] < 0) {
+            return nullptr;
+        }
+    }
+    return new SkDashPathEffect(intervals, count, phase);
+}