Revert of Disable Precompile-platform with clang-cl.

third_party/WebKit/Source/core/BUILD.gn

 # Copyright 2014 The Chromium Authors. All rights reserved.
 # Use of this source code is governed by a BSD-style license that can be
 # found in the LICENSE file.
 
 import("//build/config/chromecast_build.gni")
 import("//build/toolchain/toolchain.gni")
 import("//build/config/ui.gni")
 import("//build/split_static_library.gni")
 import("//testing/libfuzzer/fuzzer_test.gni")
 import("//third_party/WebKit/Source/bindings/bindings.gni")
@@ skipping 34 matching lines @@
   ]
   if (is_android && use_openmax_dl_fft) {
     include_dirs += [ "//third_party/openmax_dl" ]
   }
 }
 
 import("//build/config/pch.gni")
 
 config("blink_core_pch") {
   if (enable_precompiled_headers) {
-    # TODO(thakis): Enable for clang once it works, https://crbug.com/667891
-    if (is_win && !is_clang) {
+    if (is_win) {
       # This is a string rather than a file GN knows about. It has to match
       # exactly what's in the /FI flag below, and what might appear in the
       # source code in quotes for an #include directive.
       precompiled_header = rebase_path("win/Precompile-core.h", root_build_dir)
 
       # This is a file that GN will compile with the above header. It will be
       # implicitly added to the sources (potentially multiple times, with one
       # variant for each language used in the target).
       precompiled_source =
           "//third_party/WebKit/Source/core/win/Precompile-core.cpp"
@@ skipping 1329 matching lines @@
   sources = [
     "frame/csp/ContentSecurityPolicyFuzzer.cpp",
   ]
   deps = [
     ":core",
     "//third_party/WebKit/Source/platform:blink_fuzzer_test_support",
   ]
   dict = "//testing/libfuzzer/fuzzers/dicts/content_security_policy.dict"
   seed_corpus = "//testing/libfuzzer/fuzzers/content_security_policy_corpus"
 }