Add some unittests for DoubleToString.

base/string_number_conversions_unittest.cc

Index: base/string_number_conversions_unittest.cc
diff --git a/base/string_number_conversions_unittest.cc b/base/string_number_conversions_unittest.cc
index 438db077a953225adac1d4bf9c8881aca750cb5b..7fbf94e2a73c0648d05a8173664ef4cdb715f4f7 100644
--- a/base/string_number_conversions_unittest.cc
+++ b/base/string_number_conversions_unittest.cc
@@ -344,6 +344,36 @@ TEST(StringNumberConversionsTest, StringToDouble) {
   EXPECT_DOUBLE_EQ(3.14, output);
 }
 
+TEST(StringNumberConversionsTest, DoubleToString) {
+  static const struct {
+    double input;
+    const char* expected;
+  } cases[] = {
+    {0.0, "0"},
+    {1.25, "1.25"},
+    {1.33518e+012, "1.33518e+12"},
+    {1.33489e+012, "1.33489e+12"},
+    {1.33505e+012, "1.33505e+12"},
+    {1.33545e+009, "1335450000"},
+    {1.33503e+009, "1335030000"},
+  };
+
+  for (size_t i = 0; i < ARRAYSIZE_UNSAFE(cases); ++i) {
+    EXPECT_EQ(cases[i].expected, DoubleToString(cases[i].input));
+  }
+
+  // The following two values were seen in crashes in the wild.
+  const char input_bytes[8] = {0, 0, 0, 0, '\xee', '\x6d', '\x73', '\x42'};
+  double input = 0;
+  memcpy(&input, input_bytes, arraysize(input_bytes));
+  EXPECT_EQ("1335179083776", DoubleToString(input));
+  const char input_bytes2[8] =
+      {0, 0, 0, '\xa0', '\xda', '\x6c', '\x73', '\x42'};
+  input = 0;
+  memcpy(&input, input_bytes2, arraysize(input_bytes2));
+  EXPECT_EQ("1334890332160", DoubleToString(input));
+}
+
 TEST(StringNumberConversionsTest, HexEncode) {
   std::string hex(HexEncode(NULL, 0));
   EXPECT_EQ(hex.length(), 0U);