Make PepperTryCatch hold a reference on PepperPluginInstanceImpl

content/renderer/pepper/pepper_try_catch.h

 // Copyright 2014 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.
 
 #ifndef CONTENT_RENDERER_PEPPER_PEPPER_TRY_CATCH_H_
 #define CONTENT_RENDERER_PEPPER_PEPPER_TRY_CATCH_H_
 
 #include "base/basictypes.h"
 #include "content/common/content_export.h"
 #include "content/renderer/pepper/v8_var_converter.h"
 #include "ppapi/c/pp_var.h"
 #include "ppapi/shared_impl/scoped_pp_var.h"
 #include "v8/include/v8.h"
 
 namespace content {
 
 class PepperPluginInstanceImpl;
 
 // Base class for scripting TryCatch helpers.
 class CONTENT_EXPORT PepperTryCatch {
  public:
+  // PepperTryCatch objects should only be used as stack variables. This object
+  // takes a reference on the given PepperPluginInstanceImpl.
   PepperTryCatch(PepperPluginInstanceImpl* instance,
                  V8VarConverter::AllowObjectVars convert_objects);
   virtual ~PepperTryCatch();
 
   virtual void SetException(const char* message) = 0;
   virtual bool HasException() = 0;
   // Gets the plugin context. Virtual so it can be overriden for testing.
   virtual v8::Handle<v8::Context> GetContext();
 
   // Convenience functions for doing conversions to/from V8 values and sets an
   // exception if there is an error in the conversion.
   v8::Handle<v8::Value> ToV8(PP_Var var);
   ppapi::ScopedPPVar FromV8(v8::Handle<v8::Value> v8_value);
 
  protected:
-  PepperPluginInstanceImpl* instance_;
+  // Make sure that |instance_| is alive for the lifetime of PepperTryCatch.
+  // PepperTryCatch is used mostly in Pepper scripting code, where it can be
+  // possible to enter JavaScript synchronously which can cause the plugin to
+  // be deleted.
+  //
+  // Note that PepperTryCatch objects should only ever be on the stack, so this
+  // shouldn't keep the instance around for too long.
+  scoped_refptr<PepperPluginInstanceImpl> instance_;
 
   // Whether To/FromV8 should convert object vars. If set to
   // kDisallowObjectVars, an exception should be set if they are encountered
   // during conversion.
   V8VarConverter::AllowObjectVars convert_objects_;
 };
 
 // Catches var exceptions and emits a v8 exception.
 class PepperTryCatchV8 : public PepperTryCatch {
  public:
@@ skipping 41 matching lines @@
 
   PP_Var* exception_;
   bool exception_is_set_;
 
   DISALLOW_COPY_AND_ASSIGN(PepperTryCatchVar);
 };
 
 }  // namespace content
 
 #endif  // CONTENT_RENDERER_PEPPER_PEPPER_TRY_CATCH_H_