Add alternative ambient shadow method to Android shadow sample

src/gpu/batches/GrAnalyticRectBatch.cpp

 /*
  * Copyright 2016 Google Inc.
  *
  * Use of this source code is governed by a BSD-style license that can be
  * found in the LICENSE file.
  */
 
 #include "GrAnalyticRectBatch.h"
 
 #include "GrBatchFlushState.h"
@@ skipping 165 matching lines @@
                 fragBuilder->codeAppend( "if (heightDistance < widthDistance) {");
                 fragBuilder->codeAppendf("    dvAxis = %s.zw;", rectEdgeVary.fsIn());
                 fragBuilder->codeAppend( "    dvLength = heightDistance;");
                 fragBuilder->codeAppend( "} else {");
                 fragBuilder->codeAppendf("    dvAxis = vec2(-%s.w, %s.z);",
                                          rectEdgeVary.fsIn(), rectEdgeVary.fsIn());
                 fragBuilder->codeAppend( "    dvLength = widthDistance;");
                 fragBuilder->codeAppend( "}");
 
                 fragBuilder->codeAppend( "float dvSign = sign(dot(offset, dvAxis));");
-                fragBuilder->codeAppendf("%s = vec3(dvSign * dvAxis, dvLength);",
+                fragBuilder->codeAppendf("%s = vec4(dvSign * dvAxis, dvLength, 0.0);",
                                          args.fDistanceVectorName);
 
             }
         }
 
         static void GenKey(const GrGeometryProcessor& gp,
                            const GrGLSLCaps&,
                            GrProcessorKeyBuilder* b) {
             b->add32(0x0);
         }
@@ skipping 208 matching lines @@
 DRAW_BATCH_TEST_DEFINE(AnalyticRectBatch) {
     SkMatrix viewMatrix = GrTest::TestMatrix(random);
     GrColor color = GrRandomColor(random);
     SkRect rect = GrTest::TestSquare(random);
     SkRect croppedRect = GrTest::TestSquare(random);
     SkRect bounds = GrTest::TestSquare(random);
     return new AnalyticRectBatch(color, viewMatrix, rect, croppedRect, bounds);
 }
 
 #endif