Convert serialized values to ints if they are whole and less than 53 bits.

Source/bindings/dart/DartUtilities.cpp

 // Copyright 2011, Google Inc.
 // All rights reserved.
 //
 // Redistribution and use in source and binary forms, with or without
 // modification, are permitted provided that the following conditions are
 // met:
 //
 //    * Redistributions of source code must retain the above copyright
 // notice, this list of conditions and the following disclaimer.
 //    * Redistributions in binary form must reproduce the above
@@ skipping 22 matching lines @@
 #include "DartBlob.h"
 #include "DartHTMLElement.h"
 #include "DartIDBKeyRange.h"
 #include "DartImageData.h"
 #include "DartMessagePort.h"
 #include "bindings/dart/DartDOMData.h"
 #include "bindings/dart/DartHandleProxy.h"
 #include "bindings/dart/V8Converter.h"
 #include "bindings/v8/ScriptController.h"
 #include "bindings/v8/SerializedScriptValue.h"
+#include "bindings/v8/V8Binding.h"
 #include "core/dom/Document.h"
 #include "core/html/canvas/DataView.h"
 #include "core/inspector/ScriptArguments.h"
 #include "core/inspector/ScriptCallStack.h"
 #include "core/loader/FrameLoader.h"
 #include "core/page/DOMWindow.h"
 #include "core/page/Frame.h"
 #include "core/platform/network/ResourceRequest.h"
 #include "core/platform/sql/SQLValue.h"
 
@@ skipping 221 matching lines @@
         return 0;
     if (value < 0) {
         exception = Dart_NewStringFromCString("value out of range");
         return 0;
     }
     return value;
 }
 
 Dart_Handle DartUtilities::numberToDart(double value)
 {
-    int intValue = static_cast<int>(value);
-    if (value == intValue)
-        return intToDart(intValue);
+    // JS can store integer values that are no greater than 2^53 - 1.
+    if (value <= kJSMaxInteger && value >= -kJSMaxInteger) {

[sra1, 2013/10/18 02:56:28]

nit: This would be slightly more readable:

if (-k <= value && value <= k) ...

+        int64_t intValue = static_cast<int64_t>(value);
+        if (value == intValue)
+            return intToDart(intValue);
+    }
     return doubleToDart(value);
 }
 
 ScriptValue DartUtilities::dartToScriptValue(Dart_Handle object, Dart_Handle& exception)
 {
     return ScriptValue(V8Converter::toV8(object, exception));
 }
 
 Dart_Handle DartUtilities::scriptValueToDart(const ScriptValue& value)
 {
@@ skipping 802 matching lines @@
     Dart_PersistentHandle library = domData->htmlLibrary();
     ASSERT(!Dart_IsError(library));
 
     Dart_Handle utilsClass = Dart_GetType(library, Dart_NewStringFromCString("_Utils"), 0, 0);
     ASSERT(!Dart_IsError(utilsClass));
 
     return Dart_Invoke(utilsClass, Dart_NewStringFromCString(methodName), argCount, args);
 }
 
 }