refactor DM::SetupBitmap

Seemed sort of repetitive.

BUG=skia:
R=reed@google.com, mtklein@google.com

Author: mtklein@chromium.org

Review URL: https://codereview.chromium.org/286993005

git-svn-id: http://skia.googlecode.com/svn/trunk@14752 2bbb7eff-a529-9590-31e7-b0007b416f81
diff --git a/dm/DMCpuGMTask.cpp b/dm/DMCpuGMTask.cpp
index eb7ed99..add5b38 100644
--- a/dm/DMCpuGMTask.cpp
+++ b/dm/DMCpuGMTask.cpp
@@ -26,7 +26,7 @@
 
 void CpuGMTask::draw() {
     SkBitmap bitmap;
-    SetupBitmap(fColorType, fGM.get(), &bitmap);
+    AllocatePixels(fColorType, fGM->getISize().width(), fGM->getISize().height(), &bitmap);
 
     SkCanvas canvas(bitmap);
     canvas.concat(fGM->getInitialTransform());