Reverting r4329 due to failure in webkit tests.

src/runtime.cc

Index: src/runtime.cc
===================================================================
--- src/runtime.cc	(revision 4329)
+++ src/runtime.cc	(working copy)
@@ -4686,9 +4686,49 @@
 
   s->TryFlatten();
 
-  RUNTIME_ASSERT(radix == 0 || (2 <= radix && radix <= 36));
-  double value = StringToInt(s, radix);
-  return Heap::NumberFromDouble(value);
+  int len = s->length();
+  int i;
+
+  // Skip leading white space.
+  for (i = 0; i < len && Scanner::kIsWhiteSpace.get(s->Get(i)); i++) ;
+  if (i == len) return Heap::nan_value();
+
+  // Compute the sign (default to +).
+  int sign = 1;
+  if (s->Get(i) == '-') {
+    sign = -1;
+    i++;
+  } else if (s->Get(i) == '+') {
+    i++;
+  }
+
+  // Compute the radix if 0.
+  if (radix == 0) {
+    radix = 10;
+    if (i < len && s->Get(i) == '0') {
+      radix = 8;
+      if (i + 1 < len) {
+        int c = s->Get(i + 1);
+        if (c == 'x' || c == 'X') {
+          radix = 16;
+          i += 2;
+        }
+      }
+    }
+  } else if (radix == 16) {
+    // Allow 0x or 0X prefix if radix is 16.
+    if (i + 1 < len && s->Get(i) == '0') {
+      int c = s->Get(i + 1);
+      if (c == 'x' || c == 'X') i += 2;
+    }
+  }
+
+  RUNTIME_ASSERT(2 <= radix && radix <= 36);
+  double value;
+  int end_index = StringToInt(s, i, radix, &value);
+  if (end_index != i) {
+    return Heap::NumberFromDouble(sign * value);
+  }
   return Heap::nan_value();
 }