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

Source/bindings/dart/DartUtilities.cpp

Index: Source/bindings/dart/DartUtilities.cpp
diff --git a/Source/bindings/dart/DartUtilities.cpp b/Source/bindings/dart/DartUtilities.cpp
index 9326acf8ac5292d6643a7773997d8daa950da27b..3eaf9ff2a50196a7fa4268086fe7fe464fd0542e 100644
--- a/Source/bindings/dart/DartUtilities.cpp
+++ b/Source/bindings/dart/DartUtilities.cpp
@@ -40,6 +40,7 @@
 #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"
@@ -281,9 +282,12 @@ unsigned long long DartUtilities::dartToUnsignedLongLong(Dart_Handle object, Dar
 
 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);
 }