Stop overwriting errno in base::StringPrintf, StringAppendV, and StringToDouble

base/strings/string_number_conversions_unittest.cc

Index: base/strings/string_number_conversions_unittest.cc
diff --git a/base/strings/string_number_conversions_unittest.cc b/base/strings/string_number_conversions_unittest.cc
index 4d413d768ac5a35d41e2ca14245a06904d86f0e7..5ae59d304108a865fb994143f58aa091b03b2b5d 100644
--- a/base/strings/string_number_conversions_unittest.cc
+++ b/base/strings/string_number_conversions_unittest.cc
@@ -2,6 +2,7 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+#include <errno.h>
 #include <math.h>
 
 #include <limits>
@@ -449,7 +450,10 @@ TEST(StringNumberConversionsTest, StringToDouble) {
 
   for (size_t i = 0; i < ARRAYSIZE_UNSAFE(cases); ++i) {
     double output;
+    errno = 1;
     EXPECT_EQ(cases[i].success, StringToDouble(cases[i].input, &output));
+    if (cases[i].success)
+      EXPECT_EQ(1, errno) << i;  // confirm that errno is unchanged.
     EXPECT_DOUBLE_EQ(cases[i].output, output);
   }