Bump protobuf version

This is to pick up changes to remove deprecated use of `is_pod<>`.

The CMakeLists.txt file has moved to the root directory. Add some new
warning suppressions.

Change-Id: Id58fc9a8e9e467accd877c7b58f80331a2f5f0c6
Reviewed-on: https://dawn-review.googlesource.com/c/dawn/+/148082
Auto-Submit: James Price <jrprice@google.com>
Reviewed-by: Ben Clayton <bclayton@google.com>
Commit-Queue: James Price <jrprice@google.com>
Kokoro: Kokoro <noreply+kokoro@google.com>
diff --git a/DEPS b/DEPS
index 246e930..f3859fc 100644
--- a/DEPS
+++ b/DEPS
@@ -257,7 +257,7 @@
 
   # Misc dependencies inherited from Tint
   'third_party/protobuf': {
-    'url': '{chromium_git}/external/github.com/protocolbuffers/protobuf.git@fde7cf7358ec7cd69e8db9be4f1fa6a5c431386a',
+    'url': '{chromium_git}/external/github.com/protocolbuffers/protobuf.git@2b673bbb57e34fe1bd4570f726fc86b769a3a3d2',
     'condition': 'dawn_standalone',
   },
 }