Add alternative ambient shadow method to Android shadow sample

src/gpu/GrOvalRenderer.cpp

Index: src/gpu/GrOvalRenderer.cpp
diff --git a/src/gpu/GrOvalRenderer.cpp b/src/gpu/GrOvalRenderer.cpp
index 89e35a1d707d49160005db46d0d289b66fc7bfad..307fee08dc61bf2c26b5bb18e3749f6d13e8f422 100644
--- a/src/gpu/GrOvalRenderer.cpp
+++ b/src/gpu/GrOvalRenderer.cpp
@@ -129,20 +129,23 @@ public:
                                  args.fTransformsOut);
 
             fragBuilder->codeAppendf("float d = length(%s.xy);", v.fsIn());
-            fragBuilder->codeAppendf("float distanceToEdge = %s.z * (1.0 - d);", v.fsIn());
-            fragBuilder->codeAppendf("float edgeAlpha = clamp(distanceToEdge, 0.0, 1.0);");
+            fragBuilder->codeAppendf("float distanceToOuterEdge = %s.z * (1.0 - d);", v.fsIn());
+            fragBuilder->codeAppendf("float edgeAlpha = clamp(distanceToOuterEdge, 0.0, 1.0);");
             if (cgp.fStroke) {
-                fragBuilder->codeAppendf("float innerAlpha = clamp(%s.z * (d - %s.w), 0.0, 1.0);",
+                fragBuilder->codeAppendf("float distanceToInnerEdge = %s.z * (d - %s.w);",
                                          v.fsIn(), v.fsIn());
+                fragBuilder->codeAppend("float innerAlpha = clamp(distanceToInnerEdge, 0.0, 1.0);");
                 fragBuilder->codeAppend("edgeAlpha *= innerAlpha;");
             }
 
             if (args.fDistanceVectorName) {
                 fragBuilder->codeAppend ("if (d == 0.0) {"); // if on the center of the circle
-                fragBuilder->codeAppendf("    %s = vec3(1.0, 0.0, distanceToEdge);", // no normalize
+                fragBuilder->codeAppendf("    %s = vec4(1.0, 0.0, distanceToOuterEdge, "
+                                         "distanceToInnerEdge);", // no normalize
                                          args.fDistanceVectorName);
                 fragBuilder->codeAppend ("} else {");
-                fragBuilder->codeAppendf("    %s = vec3(normalize(%s.xy), distanceToEdge);",
+                fragBuilder->codeAppendf("    %s = vec4(normalize(%s.xy), distanceToOuterEdge, "
+                                         "distanceToInnerEdge);",
                                          args.fDistanceVectorName, v.fsIn());
                 fragBuilder->codeAppend ("}");
             }