Reset scoped_ptr to make plugin crash on higher level.

pdf/instance.cc

Index: pdf/instance.cc
diff --git a/pdf/instance.cc b/pdf/instance.cc
index a17db57ae93d77014202fabde522aa94551f28b2..7e626484ae7ee0a33fe808ba524ed32938851aee 100644
--- a/pdf/instance.cc
+++ b/pdf/instance.cc
@@ -308,6 +308,10 @@ Instance::Instance(PP_Instance instance)
 
 Instance::~Instance() {
   RemovePerInstanceObject(kPPPPdfInterface, this);
+  // TODO(vitalybuka): remove after crbug.com/372095 fixed.
+  // Reset to NULL to make it crash in HandleDocumentLoad if called for
+  // deleted instance. scoped_ptr::~scoped_ptr does not reset pointer to NULL.
+  engine_.reset();
 }
 
 bool Instance::Init(uint32_t argc, const char* argn[], const char* argv[]) {