Roll clang 296320:296321.

This rolls by just one revision, which happens to be a no-op change.
What's new (other than picking up recent plugin changes) is that
the packager now uploaded PDBs for Windows to chromium-browser-symsrv.

BUG=682500

Review-Url: https://codereview.chromium.org/2738253002
Cr-Commit-Position: refs/heads/master@{#455977}

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 = '296320'
+CLANG_REVISION = '296321'
 
 use_head_revision = 'LLVM_FORCE_HEAD_REVISION' in os.environ
 if use_head_revision: