fix misc asserts and checks found by fuzzer

BUG=skia:
GOLD_TRYBOT_URL= https://gold.skia.org/search2?unt=true&query=source_type%3Dgm&master=false&issue=1719993002

Review URL: https://codereview.chromium.org/1719993002

4 files changed, 21 insertions, 12 deletions

diff --git a/include/core/SkPathEffect.h b/include/core/SkPathEffect.h
index bd68c8fa72..a77b9467e4 100644
--- a/include/core/SkPathEffect.h
+++ b/include/core/SkPathEffect.h
@@ -183,7 +183,13 @@ public:
         The reference counts for outer and inner are both incremented in the constructor,
         and decremented in the destructor.
     */
-    static SkComposePathEffect* Create(SkPathEffect* outer, SkPathEffect* inner) {
+    static SkPathEffect* Create(SkPathEffect* outer, SkPathEffect* inner) {
+        if (!outer) {
+            return SkSafeRef(inner);
+        }
+        if (!inner) {
+            return SkSafeRef(outer);
+        }
         return new SkComposePathEffect(outer, inner);
     }
 
@@ -220,7 +226,13 @@ public:
         The reference counts for first and second are both incremented in the constructor,
         and decremented in the destructor.
     */
-    static SkSumPathEffect* Create(SkPathEffect* first, SkPathEffect* second) {
+    static SkPathEffect* Create(SkPathEffect* first, SkPathEffect* second) {
+        if (!first) {
+            return SkSafeRef(second);
+        }
+        if (!second) {
+            return SkSafeRef(first);
+        }
         return new SkSumPathEffect(first, second);
     }
 
diff --git a/include/effects/Sk1DPathEffect.h b/include/effects/Sk1DPathEffect.h
index 3419dc23b7..03c6966943 100644
--- a/include/effects/Sk1DPathEffect.h
+++ b/include/effects/Sk1DPathEffect.h
@@ -46,7 +46,7 @@ public:
         kRotate_Style,      // rotate the shape about its center
         kMorph_Style,       // transform each point, and turn lines into curves
 
-        kStyleCount
+        kLastEnum_Style = kMorph_Style,
     };
 
     /** Dash by replicating the specified path.
@@ -56,9 +56,7 @@ public:
         @param style how to transform path at each point (based on the current
                      position and tangent)
     */
-    static SkPathEffect* Create(const SkPath& path, SkScalar advance, SkScalar phase, Style style) {
-        return new SkPath1DPathEffect(path, advance, phase, style);
-    }
+    static SkPathEffect* Create(const SkPath& path, SkScalar advance, SkScalar phase, Style);
 
     virtual bool filterPath(SkPath*, const SkPath&,
                             SkStrokeRec*, const SkRect*) const override;
diff --git a/include/effects/SkAlphaThresholdFilter.h b/include/effects/SkAlphaThresholdFilter.h
index 17521b6455..033e8d1e54 100644
--- a/include/effects/SkAlphaThresholdFilter.h
+++ b/include/effects/SkAlphaThresholdFilter.h
@@ -20,8 +20,8 @@ public:
      * The 0,0 point of the region corresponds to the upper left corner of the
      * source image.
      */
-    static SkImageFilter* Create(const SkRegion& region, SkScalar innerThreshold,
-                                 SkScalar outerThreshold, SkImageFilter* input = NULL);
+    static SkImageFilter* Create(const SkRegion& region, SkScalar innerMin,
+                                 SkScalar outerMax, SkImageFilter* input = NULL);
     SK_DECLARE_FLATTENABLE_REGISTRAR_GROUP();
 };
 
diff --git a/include/effects/SkDashPathEffect.h b/include/effects/SkDashPathEffect.h
index 3c1407b725..08b0a4693f 100644
--- a/include/effects/SkDashPathEffect.h
+++ b/include/effects/SkDashPathEffect.h
@@ -36,10 +36,7 @@ public:
 
         Note: only affects stroked paths.
     */
-    static SkPathEffect* Create(const SkScalar intervals[], int count, SkScalar phase) {
-        return new SkDashPathEffect(intervals, count, phase);
-    }
-    virtual ~SkDashPathEffect();
+    static SkPathEffect* Create(const SkScalar intervals[], int count, SkScalar phase);
 
     virtual bool filterPath(SkPath* dst, const SkPath& src,
                             SkStrokeRec*, const SkRect*) const override;
@@ -58,6 +55,7 @@ public:
 #endif
 
 protected:
+    virtual ~SkDashPathEffect();
     SkDashPathEffect(const SkScalar intervals[], int count, SkScalar phase);
     void flatten(SkWriteBuffer&) const override;
 
@@ -66,6 +64,7 @@ private:
     int32_t     fCount;
     SkScalar    fPhase;
     // computed from phase
+
     SkScalar    fInitialDashLength;
     int32_t     fInitialDashIndex;
     SkScalar    fIntervalLength;