[D8] Clean up a few things.

- Remove unnecessary LSAN #include.
- Use i:: instead of internal:: for consistency.

Bug: 
Change-Id: I783b28402bf9c661e51b629167ec73b98a6b9fd7
Reviewed-on: https://chromium-review.googlesource.com/818198Reviewed-by: Michael Lippautz <mlippautz@chromium.org>
Commit-Queue: Bill Budge <bbudge@chromium.org>
Cr-Commit-Position: refs/heads/master@{#49979}

src/d8.cc

@@ -41,10 +41,6 @@
 #include "src/utils.h"
 #include "src/v8.h"
 
-#if defined(LEAK_SANITIZER)
-#include <sanitizer/lsan_interface.h>
-#endif
-
 #if !defined(_WIN32) && !defined(_WIN64)
 #include <unistd.h>  // NOLINT
 #else
@@ -2235,7 +2231,7 @@ Local<String> Shell::ReadFile(Isolate* isolate, const char* name) {
   char* chars = ReadChars(name, &size);
   if (chars == nullptr) return Local<String>();
   Local<String> result;
-  if (i::FLAG_use_external_strings && internal::String::IsAscii(chars, size)) {
+  if (i::FLAG_use_external_strings && i::String::IsAscii(chars, size)) {
     String::ExternalOneByteStringResource* resource =
         new ExternalOwningOneByteStringResource(
             std::unique_ptr<const char[]>(chars), size);