Make the file chooser use PP_ArrayOutput

ppapi/cpp/array_output.h

 // Copyright (c) 2012 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 PPAPI_CPP_ARRAY_OUTPUT_H_
 #define PPAPI_CPP_ARRAY_OUTPUT_H_
 
 #include <vector>
 
 #include "ppapi/c/pp_array_output.h"
@@ skipping 29 matching lines @@
 // derived classes below.
 class ArrayOutputAdapterBase {
  public:
   ArrayOutputAdapterBase() {
     pp_array_output_.GetDataBuffer =
         &ArrayOutputAdapterBase::GetDataBufferThunk;
     pp_array_output_.user_data = this;
   }
   virtual ~ArrayOutputAdapterBase() {}
 
-  PP_ArrayOutput* pp_array_output() { return &pp_array_output_; }
+  const PP_ArrayOutput& pp_array_output() { return pp_array_output_; }
 
  protected:
   virtual void* GetDataBuffer(uint32_t element_count,
                               uint32_t element_size) = 0;
 
  private:
   static void* GetDataBufferThunk(void* user_data,
                                   uint32_t element_count,
                                   uint32_t element_size);
 
@@ skipping 24 matching lines @@
  public:
   ArrayOutputAdapter(std::vector<T>* output) : output_(output) {}
 
  protected:
   // Two-step init for the "with storage" version below.
   ArrayOutputAdapter() : output_(NULL) {}
   void set_output(std::vector<T>* output) { output_ = output; }
 
   // ArrayOutputAdapterBase implementation.
   virtual void* GetDataBuffer(uint32_t element_count, uint32_t element_size) {
+    if (element_count == 0)
+      return NULL;
     PP_DCHECK(element_size == sizeof(T));
     if (element_size != sizeof(T))
       return NULL;
     output_->resize(element_count);
     return &(*output_)[0];
   }
 
  private:
   std::vector<T>* output_;
 };
@@ skipping 28 matching lines @@
   }
 
  protected:
   // Two-step init for the "with storage" version below.
   ResourceArrayOutputAdapter() : output_(NULL) {}
   void set_output(T* output) { output_ = output; }
 
   // ArrayOutputAdapterBase implementation.
   virtual void* GetDataBuffer(uint32_t element_count,
                               uint32_t element_size) {
+    if (element_count == 0)
+      return NULL;
     PP_DCHECK(element_size == sizeof(PP_Resource));
     if (element_size != sizeof(PP_Resource))
       return NULL;
     intermediate_output_.resize(element_count);
     return &intermediate_output_[0];
   }
 
  private:
   std::vector<PP_Resource> intermediate_output_;
   std::vector<T>* output_;
@@ skipping 98 matching lines @@
   std::vector<PP_Resource> temp_storage_;
 
   // When asked for the output, the resources above will be converted to the
   // C++ resource objects in this array for passing to the calling code.
   std::vector<T> output_storage_;
 };
 
 }  // namespace pp
 
 #endif  // PPAPI_CPP_ARRAY_OUTPUT_H_