add installPixels

BUG=skia:
R=halcanary@google.com

Review URL: https://codereview.chromium.org/143073008

git-svn-id: http://skia.googlecode.com/svn/trunk@13174 2bbb7eff-a529-9590-31e7-b0007b416f81
diff --git a/src/utils/SkPDFRasterizer.cpp b/src/utils/SkPDFRasterizer.cpp
index 68a3119..6663480 100644
--- a/src/utils/SkPDFRasterizer.cpp
+++ b/src/utils/SkPDFRasterizer.cpp
@@ -50,8 +50,7 @@
   char *imgData = image.data();
 
   SkBitmap bitmap;
-  bitmap.setConfig(SkBitmap::kARGB_8888_Config, width, height);
-  if (!bitmap.allocPixels()) {
+  if (!bitmap.allocPixels(SkImageInfo::MakeN32Premul(width, height))) {
     return false;
   }
   bitmap.eraseColor(SK_ColorWHITE);