Replace string copy code and scoped_arrays() with const_casts in MediaDeviceNotificationsLinuxTest.

chrome/browser/media_gallery/media_device_notifications_linux_unittest.cc

Index: chrome/browser/media_gallery/media_device_notifications_linux_unittest.cc
===================================================================
--- chrome/browser/media_gallery/media_device_notifications_linux_unittest.cc	(revision 132699)
+++ chrome/browser/media_gallery/media_device_notifications_linux_unittest.cc	(working copy)
@@ -39,19 +39,6 @@
 const char kMountPointA[] = "mnt_a";
 const char kMountPointB[] = "mnt_b";
 
-// TODO(thestig) Move this into base/string_util.h, or replace this with
-// strndup_with_new() if we find more uses for it.
-// Duplicate the content of |str| into a new char array. Caller takes ownership
-// of the allocated array. Unlike std::string::c_str(), this returns a char*
-// instead of a const char*.
-char* copy_string(const std::string& str) {
-  const size_t len = str.length();
-  char* ret = new char[len + 1];
-  str.copy(ret, len, 0);
-  ret[len] = '\0';
-  return ret;
-}
-
 class MediaDeviceNotificationsLinuxTestWrapper
     : public MediaDeviceNotificationsLinux {
  public:
@@ -198,18 +185,27 @@
     FILE* file = setmntent(mtab_file_.value().c_str(), overwrite ? "w" : "a");
     ASSERT_TRUE(file);
 
+    // Due to the glibc *mntent() design, which is out of our control, the
+    // mtnent struct has several char* fields, even though we do not write to

[vandebo (ex-Chrome), 2012/04/18 00:01:50]

nit: we -> it

+    // them in the calls below. To make the compiler happy while avoiding making
+    // additional copies of strings, we just const_cast() the strings' c_str()s.
+    // This is safe since addmntent() does not write to the char* fields.
+    // In case there is an addmntent() implementation that does change the
+    // fields in question, it will crash if it tries to wrote to the mnt_opts

[vandebo (ex-Chrome), 2012/04/18 00:01:50]

nit: wrote -> write

+    // field. If such an implementation writes to the other char* fields, that
+    // is ok because each MtabTestData struct is used only once. All the fields
+    // in the MtabTestData structs are constructed from C strings and not from
+    // other std::strings, so there is no std::string COW issues to worry about
+    // either.
     mntent entry;
-    scoped_array<char> mount_opts(copy_string("rw"));
-    entry.mnt_opts = mount_opts.get();
+    static const char kMountOpts[] = "rw";
+    entry.mnt_opts = const_cast<char*>(kMountOpts);
     entry.mnt_freq = 0;
     entry.mnt_passno = 0;
     for (size_t i = 0; i < data_size; ++i) {
-      scoped_array<char> mount_device(copy_string(data[i].mount_device));
-      scoped_array<char> mount_point(copy_string(data[i].mount_point));
-      scoped_array<char> mount_type(copy_string(data[i].mount_type));
-      entry.mnt_fsname = mount_device.get();
-      entry.mnt_dir = mount_point.get();
-      entry.mnt_type = mount_type.get();
+      entry.mnt_fsname = const_cast<char*>(data[i].mount_device.c_str());
+      entry.mnt_dir = const_cast<char*>(data[i].mount_point.c_str());
+      entry.mnt_type = const_cast<char*>(data[i].mount_type.c_str());
       ASSERT_EQ(0, addmntent(file, &entry));
     }
     ASSERT_EQ(1, endmntent(file));
@@ -337,9 +333,13 @@
   // Detach |kDevice1| from |kMountPointB|.
   // kDevice1 -> kMountPointA
   // kDevice2 -> kMountPointB
+  MtabTestData test_data5[] = {
+    MtabTestData(kDevice1, test_path_a.value(), kValidFS),
+    MtabTestData(kDevice2, test_path_b.value(), kValidFS),
+  };
   EXPECT_CALL(observer(), OnMediaDeviceAttached(_, _, _)).Times(2);
   EXPECT_CALL(observer(), OnMediaDeviceDetached(_)).Times(1);
-  OverwriteMtabAndRunLoop(test_data1, arraysize(test_data1));
+  OverwriteMtabAndRunLoop(test_data5, arraysize(test_data5));
 
   // Detach all devices.
   EXPECT_CALL(observer(), OnMediaDeviceAttached(_, _, _)).Times(0);