Bug fix in SkPDFImage.

Need to lock the pixels to make sure they are there.

Review URL: http://codereview.appspot.com/2717041

git-svn-id: http://skia.googlecode.com/svn/trunk@615 2bbb7eff-a529-9590-31e7-b0007b416f81
diff --git a/src/pdf/SkPDFImage.cpp b/src/pdf/SkPDFImage.cpp
index b480089..65b9b24 100644
--- a/src/pdf/SkPDFImage.cpp
+++ b/src/pdf/SkPDFImage.cpp
@@ -31,6 +31,7 @@
 SkMemoryStream* extractImageData(const SkBitmap& bitmap) {
     SkMemoryStream* result;
 
+    bitmap.lockPixels();
     switch (bitmap.getConfig()) {
         case SkBitmap::kIndex8_Config:
             result = new SkMemoryStream(bitmap.getPixels(), bitmap.getSize(),
@@ -110,6 +111,7 @@
         default:
             SkASSERT(false);
     }
+    bitmap.unlockPixels();
     return result;
 }