replace setConfig+allocPixels with single call

tests/PremulAlphaRoundTripTest.cpp

Index: tests/PremulAlphaRoundTripTest.cpp
diff --git a/tests/PremulAlphaRoundTripTest.cpp b/tests/PremulAlphaRoundTripTest.cpp
index 77f62dcecd960432919cb256f7304304a3ed0e78..5e8e8bf1dd42843b8db5d9905b4812e1e4106f72 100644
--- a/tests/PremulAlphaRoundTripTest.cpp
+++ b/tests/PremulAlphaRoundTripTest.cpp
@@ -17,8 +17,7 @@
 
 static void fillCanvas(SkCanvas* canvas, SkCanvas::Config8888 unpremulConfig) {
     SkBitmap bmp;
-    bmp.setConfig(SkBitmap::kARGB_8888_Config, 256, 256);
-    bmp.allocPixels();
+    bmp.allocN32Pixels(256, 256);
     SkAutoLockPixels alp(bmp);
     uint32_t* pixels = reinterpret_cast<uint32_t*>(bmp.getPixels());
 
@@ -72,11 +71,9 @@ DEF_GPUTEST(PremulAlphaRoundTrip, reporter, factory) {
             SkCanvas canvas(device);
 
             SkBitmap readBmp1;
-            readBmp1.setConfig(SkBitmap::kARGB_8888_Config, 256, 256);
-            readBmp1.allocPixels();
+            readBmp1.allocN32Pixels(256, 256);
             SkBitmap readBmp2;
-            readBmp2.setConfig(SkBitmap::kARGB_8888_Config, 256, 256);
-            readBmp2.allocPixels();
+            readBmp2.allocN32Pixels(256, 256);
 
             for (size_t upmaIdx = 0;
                  upmaIdx < SK_ARRAY_COUNT(gUnpremulConfigs);