Revert "Use InernalAlloc in DemangleCXXABI"

This reverts commit 649004a.

This commit caused regression in TSAN tests on Darwin:
https://green.lab.llvm.org/green/job/clang-stage1-RA/35380/

These tests have been failing:
SanitizerCommon-tsan-x86_64-Darwin.Darwin.symbolizer-function-offset-dladdr.cpp
SanitizerCommon-tsan-x86_64h-Darwin.Darwin.symbolizer-function-offset-dladdr.cpp
ThreadSanitizer-x86_64.Darwin.symbolizer-dladdr.cpp
ThreadSanitizer-x86_64h.Darwin.symbolizer-dladdr.cpp

Author: hyp

compiler-rt/lib/sanitizer_common/sanitizer_symbolizer_posix_libcdep.cpp

@@ -46,20 +46,15 @@ namespace __sanitizer {
 
 // Attempts to demangle the name via __cxa_demangle from __cxxabiv1.
 const char *DemangleCXXABI(const char *name) {
-  // __cxa_demangle aggressively insists on allocating memory.
+  // FIXME: __cxa_demangle aggressively insists on allocating memory.
   // There's not much we can do about that, short of providing our
   // own demangler (libc++abi's implementation could be adapted so that
-  // it does not allocate). For now, we just call it anyway, and use
-  // InternalAlloc to prevent lsan error.
-  if (&__cxxabiv1::__cxa_demangle) {
-    if (char *demangled_name = __cxxabiv1::__cxa_demangle(name, 0, 0, 0)) {
-      size_t size = internal_strlen(demangled_name) + 1;
-      char *buf = (char *)InternalAlloc(size);
-      internal_memcpy(buf, demangled_name, size);
-      free(demangled_name);
-      return buf;
-    }
-  }
+  // it does not allocate). For now, we just call it anyway, and we leak
+  // the returned value.
+  if (&__cxxabiv1::__cxa_demangle)
+    if (const char *demangled_name =
+          __cxxabiv1::__cxa_demangle(name, 0, 0, 0))
+      return demangled_name;
 
   return name;
 }