Bug 1412416 - Part 1: Support arena duplication of wide strings. r=froydnj

This adds support for duplicating both raw `char*` strings and raw `char16_t*`
strings by making the character type generic.

--HG--
extra : rebase_source : bb5245ed71161c8c785684e5a56ac894f03874ea
extra : histedit_source : e94eb738a3982f0cb63a894a0cdfbdf0be2b9cad

xpcom/ds/ArenaAllocatorExtensions.h

@@ -32,11 +32,11 @@ T* DuplicateString(const T* aSrc, const CheckedInt<size_t>& aLen,
  * @param aArena The arena to allocate the string copy out of.
  * @return An arena allocated null-terminated string.
  */
-template<size_t ArenaSize, size_t Alignment>
-char* ArenaStrdup(const char* aStr,
-                  ArenaAllocator<ArenaSize, Alignment>& aArena)
+template<typename T, size_t ArenaSize, size_t Alignment>
+T* ArenaStrdup(const T* aStr,
+               ArenaAllocator<ArenaSize, Alignment>& aArena)
 {
-  return detail::DuplicateString(aStr, strlen(aStr), aArena);
+  return detail::DuplicateString(aStr, nsCharTraits<T>::length(aStr), aArena);
 }
 
 /**

xpcom/tests/gtest/TestArenaAllocator.cpp

@@ -284,10 +284,15 @@ TEST(ArenaAllocator, Clear)
 TEST(ArenaAllocator, Extensions)
 {
   ArenaAllocator<4096, 8> a;
-  const char* const kTestStr = "This is a test string.";
-  char* dup = mozilla::ArenaStrdup(kTestStr, a);
-  EXPECT_STREQ(dup, kTestStr);
 
+  // Test with raw strings.
+  const char* const kTestCStr = "This is a test string.";
+  char* c_dup = mozilla::ArenaStrdup(kTestCStr, a);
+  EXPECT_STREQ(c_dup, kTestCStr);
+
+  const char16_t* const kTestStr = u"This is a wide test string.";
+  char16_t* dup = mozilla::ArenaStrdup(kTestStr, a);
+  EXPECT_TRUE(nsString(dup).Equals(kTestStr));
   NS_NAMED_LITERAL_STRING(wideStr, "A wide string.");
   nsLiteralString::char_type* wide = mozilla::ArenaStrdup(wideStr, a);
   EXPECT_TRUE(wideStr.Equals(wide));