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..a79027f87443bd79f56eb6ea08ea895872f77dae 100644
--- a/Source/bindings/dart/DartUtilities.cpp
+++ b/Source/bindings/dart/DartUtilities.cpp
@@ -50,6 +50,8 @@
 #include "core/platform/network/ResourceRequest.h"
 #include "core/platform/sql/SQLValue.h"
 
+#include <math.h>
+
 #include <wtf/ArrayBufferView.h>
 #include <wtf/Float32Array.h>
 #include <wtf/Float64Array.h>
@@ -281,8 +283,9 @@ unsigned long long DartUtilities::dartToUnsignedLongLong(Dart_Handle object, Dar
 
 Dart_Handle DartUtilities::numberToDart(double value)
 {
-    int intValue = static_cast<int>(value);
-    if (value == intValue)
+    int64_t intValue = static_cast<int64_t>(value);
+    // JS can store integer values that are no greater than 2^53.
+    if (value == intValue && abs(intValue) <= pow(2, 53))

[sra1, 2013/10/17 21:40:31]

I would avoid calling pow and define a constant
kMaxExactDouble = 9007199254740991;  // 2^53-1

2^53 is the first integer that has who mathematical integers folded onto it,
hence the -1 above.  (Math.pow(2,53) == Math.pow(2,53)+1  in the chrome
console).

First compare the range because that avoids problems with infinites and NaN
values.

if (value >= -kMaxExactDouble || value <= kMaxExactDouble) {
  // now see if there is a fraction part
}

[Emily Fortuna, 2013/10/17 22:42:51]

Gotcha. Sorry I was going off of this:
http://ecma262-5.com/ELS5_HTML.htm#Section_8.5 "Note that all the positive and
negative integers whose magnitude is no greater than 253 are representable in
the Number type"

         return intToDart(intValue);
     return doubleToDart(value);
 }