Refactor the dart api a bit:

runtime/bin/file.cc

 // Copyright (c) 2011, the Dart project authors.  Please see the AUTHORS file
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
 #include "bin/file.h"
 
 #include "bin/builtin.h"
 #include "bin/dartutils.h"
 
 #include "include/dart_api.h"
@@ skipping 26 matching lines @@
       return false;
     }
     remaining -= bytes_read;  // Reduce the number of remaining bytes.
     current_buffer += bytes_read;  // Move the buffer forward.
   }
   return true;
 }
 
 
 static File* GetFileHandle(Dart_Handle fileobj) {
-  Dart_Result result = Dart_GetNativeInstanceField(fileobj, kFileFieldIndex);
-  ASSERT(Dart_IsValidResult(result));
-  File* file = reinterpret_cast<File*>(Dart_GetResultAsCIntptr(result));
+  intptr_t value = 0;
+  Dart_Handle result = Dart_GetNativeInstanceField(fileobj, kFileFieldIndex,
+                                                   &value);
+  ASSERT(Dart_IsValid(result));
+  File* file = reinterpret_cast<File*>(value);
   return file;
 }
 
 
 void FUNCTION_NAME(File_OpenFile)(Dart_NativeArguments args) {
   Dart_EnterScope();
   Dart_Handle fileobj = Dart_GetNativeArgument(args, 0);
   const char* filename =
       DartUtils::GetStringValue(Dart_GetNativeArgument(args, 1));
   bool writable = DartUtils::GetBooleanValue(Dart_GetNativeArgument(args, 2));
@@ skipping 88 matching lines @@
   Dart_EnterScope();
   intptr_t return_value = -1;
   File* file = GetFileHandle(Dart_GetNativeArgument(args, 0));
   if (file != NULL) {
     Dart_Handle buffer_obj = Dart_GetNativeArgument(args, 1);
     ASSERT(Dart_IsArray(buffer_obj));
     int64_t offset =
         DartUtils::GetIntegerValue(Dart_GetNativeArgument(args, 2));
     int64_t length =
         DartUtils::GetIntegerValue(Dart_GetNativeArgument(args, 3));
-    Dart_Result result = Dart_GetLength(buffer_obj);
-    ASSERT(Dart_IsValidResult(result));
-    ASSERT((offset + length) <= Dart_GetResultAsCIntptr(result));
+    intptr_t array_len = 0;
+    Dart_Handle result = Dart_GetLength(buffer_obj, &array_len);
+    ASSERT(Dart_IsValid(result));
+    ASSERT((offset + length) <= array_len);
     uint8_t* buffer = new uint8_t[length];
     int total_bytes_read =
         file->Read(reinterpret_cast<void*>(buffer), length);
     /*
      * Reading 0 indicates end of file.
      */
     if (total_bytes_read >= 0) {
       result =
           Dart_ArraySet(buffer_obj, offset, buffer, total_bytes_read);
-      ASSERT(Dart_IsValidResult(result));
+      ASSERT(Dart_IsValid(result));
       return_value = total_bytes_read;
     }
     delete[] buffer;
   }
   Dart_SetReturnValue(args, Dart_NewInteger(return_value));
   Dart_ExitScope();
 }
 
 
 void FUNCTION_NAME(File_WriteList)(Dart_NativeArguments args) {
   Dart_EnterScope();
   intptr_t return_value = -1;
   File* file = GetFileHandle(Dart_GetNativeArgument(args, 0));
   if (file != NULL) {
     Dart_Handle buffer_obj = Dart_GetNativeArgument(args, 1);
     ASSERT(Dart_IsArray(buffer_obj));
     int64_t offset =
         DartUtils::GetIntegerValue(Dart_GetNativeArgument(args, 2));
     int64_t length =
         DartUtils::GetIntegerValue(Dart_GetNativeArgument(args, 3));
-    Dart_Result result = Dart_GetLength(buffer_obj);
-    ASSERT(Dart_IsValidResult(result));
-    ASSERT((offset + length) <= Dart_GetResultAsCIntptr(result));
+    intptr_t buffer_len = 0;
+    Dart_Handle result = Dart_GetLength(buffer_obj, &buffer_len);
+    ASSERT(Dart_IsValid(result));
+    ASSERT((offset + length) <= buffer_len);
     uint8_t* buffer = new uint8_t[length];
     result = Dart_ArrayGet(buffer_obj, offset, buffer, length);
-    ASSERT(Dart_IsValidResult(result));
+    ASSERT(Dart_IsValid(result));
     int total_bytes_written =
         file->Write(reinterpret_cast<void*>(buffer), length);
     if (total_bytes_written >= 0) {
       return_value = total_bytes_written;
     }
     delete[] buffer;
   }
   Dart_SetReturnValue(args, Dart_NewInteger(return_value));
   Dart_ExitScope();
 }
@@ skipping 27 matching lines @@
   Dart_EnterScope();
   intptr_t return_value = -1;
   File* file = GetFileHandle(Dart_GetNativeArgument(args, 0));
   if (file != NULL) {
     file->Flush();
     return_value = 0;
   }
   Dart_SetReturnValue(args, Dart_NewInteger(return_value));
   Dart_ExitScope();
 }