MIPS: Fix NaN handling for start and end indexes in ArraySlice.

Casting NaN to int is unpredictable, on different architectures it produces different int value.

TEST=test262/S15.4.4.10_A2.1_T2, test262/S15.4.4.10_A2.2_T2

BUG=

Review URL: https://codereview.chromium.org/14812014

git-svn-id: http://v8.googlecode.com/svn/branches/bleeding_edge@14621 ce2b1a6d-e550-0410-aec6-3dcde31c8c00

src/builtins.cc

@@ -845,7 +845,7 @@ BUILTIN(ArraySlice) {
       if (start < kMinInt || start > kMaxInt) {
         return CallJsBuiltin(isolate, "ArraySlice", args);
       }
-      relative_start = static_cast<int>(start);
+      relative_start = std::isnan(start) ? 0 : static_cast<int>(start);
     } else if (!arg1->IsUndefined()) {
       return CallJsBuiltin(isolate, "ArraySlice", args);
     }
@@ -858,7 +858,7 @@ BUILTIN(ArraySlice) {
         if (end < kMinInt || end > kMaxInt) {
           return CallJsBuiltin(isolate, "ArraySlice", args);
         }
-        relative_end = static_cast<int>(end);
+        relative_end = std::isnan(end) ? 0 : static_cast<int>(end);
       } else if (!arg2->IsUndefined()) {
         return CallJsBuiltin(isolate, "ArraySlice", args);
       }