Fix print preview draft page memory leaks.

chrome/renderer/print_web_view_helper_win.cc

Index: chrome/renderer/print_web_view_helper_win.cc
diff --git a/chrome/renderer/print_web_view_helper_win.cc b/chrome/renderer/print_web_view_helper_win.cc
index 9cd72ece67ff9817f5dae4897f8cb6dcdcbcde7a..edaaf8f27391e391fcf20501d54811b80d14c7f6 100644
--- a/chrome/renderer/print_web_view_helper_win.cc
+++ b/chrome/renderer/print_web_view_helper_win.cc
@@ -140,12 +140,12 @@ void PrintWebViewHelper::RenderPreviewPage(int page_number) {
 
   // Release since |print_preview_context_| is the real owner.
   metafile.release();
-  printing::Metafile* page_metafile = NULL;
+  scoped_ptr<printing::Metafile> page_metafile;
   if (print_preview_context_.IsModifiable()) {
-    page_metafile = reinterpret_cast<printing::PreviewMetafile*>(
-        print_preview_context_.metafile())->GetMetafileForCurrentPage();
+    page_metafile.reset(reinterpret_cast<printing::PreviewMetafile*>(
+        print_preview_context_.metafile())->GetMetafileForCurrentPage());
   }
-  PreviewPageRendered(page_number, page_metafile);
+  PreviewPageRendered(page_number, page_metafile.get());
 }
 
 void PrintWebViewHelper::RenderPage(