Fix memory leak of PreviewModeClient in PDF

pdf/out_of_process_instance.cc

Index: pdf/out_of_process_instance.cc
diff --git a/pdf/out_of_process_instance.cc b/pdf/out_of_process_instance.cc
index 5f60a4bce286e7abce032d2cf657a4b03d87da62..2e62e8bde81eda1937714e5af58452bc8b8ba1c5 100644
--- a/pdf/out_of_process_instance.cc
+++ b/pdf/out_of_process_instance.cc
@@ -782,7 +782,8 @@ void OutOfProcessInstance::DidOpen(int32_t result) {
 
 void OutOfProcessInstance::DidOpenPreview(int32_t result) {
   if (result == PP_OK) {
-    preview_engine_.reset(PDFEngine::Create(new PreviewModeClient(this)));
+    preview_client_.reset(new PreviewModeClient(this));
+    preview_engine_.reset(PDFEngine::Create(preview_client_.get()));
     preview_engine_->HandleDocumentLoad(embed_preview_loader_);
   } else {
     NOTREACHED();