Fix GrConvexPolyEffect to deal with line paths.

src/gpu/effects/GrConvexPolyEffect.cpp

Index: src/gpu/effects/GrConvexPolyEffect.cpp
diff --git a/src/gpu/effects/GrConvexPolyEffect.cpp b/src/gpu/effects/GrConvexPolyEffect.cpp
index cf874cfa52604e1666ddecad3fec720d1063279a..082ea230f961a838b4b0fd9dd717d884a338252b 100644
--- a/src/gpu/effects/GrConvexPolyEffect.cpp
+++ b/src/gpu/effects/GrConvexPolyEffect.cpp
@@ -5,6 +5,7 @@
  * found in the LICENSE file.
  */
 
+#include <effects/GrConstColorProcessor.h>

[egdaniel, 2016/03/28 21:42:13]

using <...> here?

[bsalomon, 2016/03/28 21:52:54]

Ugh, my IDE inserted this without me realizing it. Will fix.

 #include "GrConvexPolyEffect.h"
 #include "GrInvariantOutput.h"
 #include "SkPathPriv.h"
@@ -254,7 +255,16 @@ GrFragmentProcessor* GrConvexPolyEffect::Create(GrPrimitiveEdgeType type, const
     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) {