Fix print preview draft page memory leaks.

chrome/renderer/print_web_view_helper_mac.mm

 // Copyright (c) 2011 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "chrome/renderer/print_web_view_helper.h"
 
 #import <AppKit/AppKit.h>
 
 #include "base/logging.h"
 #include "base/mac/scoped_nsautorelease_pool.h"
@@ skipping 50 matching lines @@
 
 void PrintWebViewHelper::RenderPreviewPage(int page_number) {
   float scale_factor = print_preview_context_.frame()->getPrintPageShrink(0);
   PrintMsg_Print_Params printParams = print_preview_context_.print_params();
   gfx::Rect content_area(printParams.margin_left, printParams.margin_top,
                          printParams.printable_size.width(),
                          printParams.printable_size.height());
 
   printing::Metafile* initial_render_metafile =
       print_preview_context_.metafile();
+  scoped_ptr<printing::Metafile> draft_metafile;
 #if !defined(USE_SKIA)
   if (print_preview_context_.IsModifiable()) {
-    initial_render_metafile = new printing::PreviewMetafile();
-    if (!initial_render_metafile->Init()) {
+    draft_metafile.reset(new printing::PreviewMetafile);
+    if (!draft_metafile->Init()) {
       DidFinishPrinting(FAIL_PREVIEW);
       return;
     }
+    initial_render_metafile = draft_metafile.get();
   }
 #endif
 
   base::TimeTicks begin_time = base::TimeTicks::Now();
   RenderPage(printParams.page_size, content_area, scale_factor, page_number,
              print_preview_context_.frame(), initial_render_metafile);
   print_preview_context_.RenderedPreviewPage(
       base::TimeTicks::Now() - begin_time);
 
-  printing::Metafile* draft_metafile = NULL;
   if (print_preview_context_.IsModifiable()) {
 #if defined(USE_SKIA)
-    draft_metafile = reinterpret_cast<printing::PreviewMetafile*>(
-        print_preview_context_.metafile())->GetMetafileForCurrentPage();
+    DCHECK(!draft_metafile.get());
+    draft_metafile.reset(reinterpret_cast<printing::PreviewMetafile*>(
+        print_preview_context_.metafile())->GetMetafileForCurrentPage());
 #else
-    draft_metafile = initial_render_metafile;
     draft_metafile->FinishDocument();
 
     // With CG, we rendered into a new metafile so we could get it as a draft
     // document.  Now we need to add it to complete document.
     draft_metafile->RenderPage(1,
                                print_preview_context_.metafile()->context(),
                                CGRectMake(content_area.x(), content_area.y(),
                                           content_area.width(),
                                           content_area.height()),
                                false /*shrunk_to_fit*/,
                                false /*stretch_to_fit*/,
                                true /*center_horizontally*/,
                                true /*center_vertically*/);
 #endif
   }
 
-  PreviewPageRendered(page_number, draft_metafile);
+  PreviewPageRendered(page_number, draft_metafile.get());
 }
 
 void PrintWebViewHelper::RenderPage(
     const gfx::Size& page_size, const gfx::Rect& content_area,
     const float& scale_factor, int page_number, WebFrame* frame,
     printing::Metafile* metafile) {
 
   {
 #if defined(USE_SKIA)
     SkDevice* device = metafile->StartPageForVectorCanvas(
@@ skipping 14 matching lines @@
     base::mac::ScopedNSAutoreleasePool pool;
     CGContextRef cgContext = metafile->context();
     CGContextRef canvasPtr = cgContext;
 #endif
     frame->printPage(page_number, canvasPtr);
   }
 
   // Done printing. Close the device context to retrieve the compiled metafile.
   metafile->FinishPage();
 }