use SkColorType instead of SkBitmap::Config in samplecode

samplecode/SampleVertices.cpp

Index: samplecode/SampleVertices.cpp
diff --git a/samplecode/SampleVertices.cpp b/samplecode/SampleVertices.cpp
index 323c4b58cb00889bd35400e1f4d04baa9e2c4ccb..4c3a17eb004bc394cbac09b961b01b492f2bd856 100644
--- a/samplecode/SampleVertices.cpp
+++ b/samplecode/SampleVertices.cpp
@@ -28,10 +28,9 @@
 static SkShader* make_shader0(SkIPoint* size) {
     SkBitmap    bm;
     size->set(2, 2);
-    bm.setConfig(SkBitmap::kARGB_8888_Config, size->fX, size->fY);
     SkPMColor color0 = SkPreMultiplyARGB(0x80, 0x80, 0xff, 0x80);
     SkPMColor color1 = SkPreMultiplyARGB(0x40, 0xff, 0x00, 0xff);
-    bm.allocPixels();
+    bm.allocN32Pixels(size->fX, size->fY);
     bm.eraseColor(color0);
     bm.lockPixels();
     uint32_t* pixels = (uint32_t*) bm.getPixels();