replace setConfig+allocPixels with single call

BUG=skia:

Review URL: https://codereview.chromium.org/162643002

git-svn-id: http://skia.googlecode.com/svn/trunk@13426 2bbb7eff-a529-9590-31e7-b0007b416f81
diff --git a/tests/ShaderOpacityTest.cpp b/tests/ShaderOpacityTest.cpp
index 5230e4a..e555603 100644
--- a/tests/ShaderOpacityTest.cpp
+++ b/tests/ShaderOpacityTest.cpp
@@ -11,8 +11,10 @@
 #include "Test.h"
 
 static void test_bitmap(skiatest::Reporter* reporter) {
+    SkImageInfo info = SkImageInfo::MakeN32Premul(2, 2);
+
     SkBitmap bmp;
-    bmp.setConfig(SkBitmap::kARGB_8888_Config, 2, 2);
+    bmp.setConfig(info);
 
     // test 1: bitmap without pixel data
     SkShader* shader = SkShader::CreateBitmapShader(bmp,
@@ -22,7 +24,7 @@
     shader->unref();
 
     // From this point on, we have pixels
-    bmp.allocPixels();
+    bmp.allocPixels(info);
 
     // test 2: not opaque by default
     shader = SkShader::CreateBitmapShader(bmp,