Make sure double to int conversion is correct.

test/cctest/test-utils.cc

Index: test/cctest/test-utils.cc
diff --git a/test/cctest/test-utils.cc b/test/cctest/test-utils.cc
index df8ff72e4f3eafed1e85aad150b2ce0d0a93f409..6cd931da4e5822e9c9368b4f16741ebdbe53c296 100644
--- a/test/cctest/test-utils.cc
+++ b/test/cctest/test-utils.cc
@@ -55,6 +55,22 @@ TEST(Utils1) {
   CHECK_EQ(-2, -8 >> 2);
   CHECK_EQ(-2, static_cast<int8_t>(-8) >> 2);
   CHECK_EQ(-2, static_cast<int>(static_cast<intptr_t>(-8) >> 2));
+
+  CHECK_EQ(-1000000, FastD2IChecked(-1000000.0));
+  CHECK_EQ(-1, FastD2IChecked(-1.0));
+  CHECK_EQ(0, FastD2IChecked(0.0));
+  CHECK_EQ(1, FastD2IChecked(1.0));
+  CHECK_EQ(1000000, FastD2IChecked(1000000.0));
+
+  CHECK_EQ(-1000000, FastD2IChecked(-1000000.123));
+  CHECK_EQ(-1, FastD2IChecked(-1.234));
+  CHECK_EQ(0, FastD2IChecked(0.345));
+  CHECK_EQ(1, FastD2IChecked(1.234));
+  CHECK_EQ(1000000, FastD2IChecked(1000000.123));
+
+  CHECK_EQ(INT_MAX, FastD2IChecked(1.0e100));
+  CHECK_EQ(INT_MIN, FastD2IChecked(-1.0e100));
+  CHECK_EQ(INT_MIN, FastD2IChecked(NAN));
 }