Roll clang 327688:328575.

Bug: 823655
Change-Id: If6dfa9d775d3be37b72b4cf5f2fd9db89763819a
Reviewed-on: https://chromium-review.googlesource.com/981314Reviewed-by: Hans Wennborg <hans@chromium.org>
Commit-Queue: Hans Wennborg <hans@chromium.org>
Cr-Commit-Position: refs/heads/master@{#546080}

build/config/compiler/BUILD.gn

@@ -1345,13 +1345,10 @@ config("default_warnings") {
 
         # TODO(hans): https://crbug.com/766891
         "-Wno-null-pointer-arithmetic",
+
+        # Ignore warnings about MSVC optimization pragmas.
+        "-Wno-ignored-pragma-optimize",
       ]
-      if (llvm_force_head_revision) {
-        cflags += [
-          # TODO(crbug.com/823655): Enable by default in next clang roll.
-          "-Wno-ignored-pragma-optimize",
-        ]
-      }
     } else if (use_xcode_clang) {
       cflags += [
         # TODO(thakis): https://crbug.com/604888

tools/clang/scripts/update.py

@@ -27,7 +27,7 @@ import zipfile
 # Do NOT CHANGE this if you don't know what you're doing -- see
 # https://chromium.googlesource.com/chromium/src/+/master/docs/updating_clang.md
 # Reverting problematic clang rolls is safe, though.
-CLANG_REVISION = '327688'
+CLANG_REVISION = '328575'
 
 use_head_revision = bool(os.environ.get('LLVM_FORCE_HEAD_REVISION', '0')
                          in ('1', 'YES'))