Fix GrConvexPolyEffect to deal with line paths.

src/gpu/effects/GrConvexPolyEffect.cpp

 /*
  * Copyright 2014 Google Inc.
  *
  * Use of this source code is governed by a BSD-style license that can be
  * found in the LICENSE file.
  */
 
 #include "GrConvexPolyEffect.h"
 #include "GrInvariantOutput.h"
 #include "SkPathPriv.h"
+#include "effects/GrConstColorProcessor.h"
 #include "glsl/GrGLSLFragmentProcessor.h"
 #include "glsl/GrGLSLFragmentShaderBuilder.h"
 #include "glsl/GrGLSLProgramDataManager.h"
 #include "glsl/GrGLSLUniformHandler.h"
 
 //////////////////////////////////////////////////////////////////////////////
 class AARectEffect : public GrFragmentProcessor {
 public:
     const SkRect& getRect() const { return fRect; }
 
@@ skipping 226 matching lines @@
     }
 
     if (path.countPoints() > kMaxEdges) {
         return nullptr;
     }
 
     SkPoint pts[kMaxEdges];
     SkScalar edges[3 * kMaxEdges];
 
     SkPathPriv::FirstDirection dir;
-    SkAssertResult(SkPathPriv::CheapComputeFirstDirection(path, &dir));
+    // The only way this should fail is if the clip is effectively a infinitely thin line. In that
+    // case nothing is inside the clip. It'd be nice to detect this at a higher level and either
+    // skip the draw or omit the clip element.
+    if (!SkPathPriv::CheapComputeFirstDirection(path, &dir)) {
+        if (GrProcessorEdgeTypeIsInverseFill(type)) {
+            return GrConstColorProcessor::Create(0xFFFFFFFF,
+                                                 GrConstColorProcessor::kModulateRGBA_InputMode);
+        }
+        return GrConstColorProcessor::Create(0, GrConstColorProcessor::kIgnore_InputMode);
+    }
 
     SkVector t;
     if (nullptr == offset) {
         t.set(0, 0);
     } else {
         t = *offset;
     }
 
     int count = path.getPoints(pts, kMaxEdges);
     int n = 0;
@@ skipping 75 matching lines @@
     }
 
     GrFragmentProcessor* fp;
     do {
         GrPrimitiveEdgeType edgeType = static_cast<GrPrimitiveEdgeType>(
                 d->fRandom->nextULessThan(kGrProcessorEdgeTypeCnt));
         fp = GrConvexPolyEffect::Create(edgeType, count, edges);
     } while (nullptr == fp);
     return fp;
 }