Remove a VC++ codegen bug workaround.

Bug: 804884,1053958
Change-Id: I7182072d3530ab3459373c6b45cca2cf753b6edc
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2063904
Commit-Queue: Nico Weber <thakis@chromium.org>
Commit-Queue: Hans Wennborg <hans@chromium.org>
Auto-Submit: Nico Weber <thakis@chromium.org>
Reviewed-by: Hans Wennborg <hans@chromium.org>
Cr-Commit-Position: refs/heads/master@{#742615}

base/strings/string_util.cc

@@ -920,11 +920,6 @@ char16* WriteInto(string16* str, size_t length_with_null) {
   return WriteIntoT(str, length_with_null);
 }
 
-#if defined(_MSC_VER) && !defined(__clang__)
-// Work around VC++ code-gen bug. https://crbug.com/804884
-#pragma optimize("", off)
-#endif
-
 // Generic version for all JoinString overloads. |list_type| must be a sequence
 // (std::vector or std::initializer_list) of strings/StringPieces (std::string,
 // string16, StringPiece or StringPiece16). |string_type| is either std::string
@@ -969,11 +964,6 @@ string16 JoinString(const std::vector<string16>& parts,
   return JoinStringT(parts, separator);
 }
 
-#if defined(_MSC_VER) && !defined(__clang__)
-// Work around VC++ code-gen bug. https://crbug.com/804884
-#pragma optimize("", on)
-#endif
-
 std::string JoinString(const std::vector<StringPiece>& parts,
                        StringPiece separator) {
   return JoinStringT(parts, separator);