Add alternative ambient shadow method to Android shadow sample

src/gpu/glsl/GrGLSLProgramBuilder.cpp

Index: src/gpu/glsl/GrGLSLProgramBuilder.cpp
diff --git a/src/gpu/glsl/GrGLSLProgramBuilder.cpp b/src/gpu/glsl/GrGLSLProgramBuilder.cpp
index 37c20deeb9c522ef73faa1e4b68aed927bd5ca51..a6bff8a85ac983fadd717d80f17ee5e4f19bc068 100644
--- a/src/gpu/glsl/GrGLSLProgramBuilder.cpp
+++ b/src/gpu/glsl/GrGLSLProgramBuilder.cpp
@@ -92,7 +92,7 @@ void GrGLSLProgramBuilder::emitAndInstallPrimProc(const GrPrimitiveProcessor& pr
         distanceVectorName = fFS.distanceVectorName();
         fFS.codeAppend( "// Normalized vector to the closest geometric edge (in device space)\n");
         fFS.codeAppend( "// Distance to the edge encoded in the z-component\n");
-        fFS.codeAppendf("vec3 %s;", distanceVectorName);
+        fFS.codeAppendf("vec4 %s;", distanceVectorName);
     }
 
     // Enclose custom code in a block to avoid namespace conflicts