Update //third_party/protobuf to version 3.

third_party/protobuf/README.chromium

Index: third_party/protobuf/README.chromium
diff --git a/third_party/protobuf/README.chromium b/third_party/protobuf/README.chromium
index 507037960d0eb6407c29d9cf03cfd189f57c717d..eb72fb991894a8322aa0018af64428fad73b90f7 100644
--- a/third_party/protobuf/README.chromium
+++ b/third_party/protobuf/README.chromium
@@ -1,52 +1,83 @@
 Name: Protocol Buffers
 Short Name: protobuf
-URL: http://protobuf.googlecode.com/svn/trunk
+URL: https://github.com/google/protobuf
 License: BSD
-License File: COPYING.txt
-Version: unknown
-Revision: r476
+License File: LICENSE
+Version: 3.0.0-beta-2
+Revision: d5fb408ddc281ffcadeb08699e65bb694656d0bd
 Security Critical: yes
 
-Local files (not taken from upstream):
-README.chromium
-config.h
-descriptor2_pb.py
+Steps used to create the current version:
+1. Pull the release from https://github.com/google/protobuf/releases
+2. Use the cleanup_release.sh script to remove unnecessary files.
+3. Add build files (BUILD.gn, proto_library.gni, protobuf.gyp,
+   protobuf_lite.gypi, protobuf_nacl.gyp).

[Peter Kasting, 2016/04/13 02:11:44]

One thing I'm concerned has been lost between my patch and yours is that mine
actually patched the build files along with the source files, and included
instructions about what should work after each successive patch.  What this
meant is that the initial set of buildfiles contained a more direct
correspondence to the upstream files, and then as we applied e.g. the
componentization patch it was clear exactly what pieces of the build file had to
do with that.  This would let a future maintainer have more confidence that they
understood what in the build files should and should not be carried forward,
because the sequential process to construct them was clear.

Now we basically just say "add the build files" with no instructions about how
to do so, increasing the likelihood that people in the future simply blindly
copy the previous buildfiles in totality, even when that wouldn't be correct.

[xyzzyz, 2016/04/14 00:23:56]

I'll update the comment to not imply to copy them blindly, but apart from that,
I don't think we can predict all issues with upstream requiring updates, so we
should just hope that the future maintainer will have good judgement. I don't
think it's worth keeping the diffs to build files, as one can always use git
history and code review comments to learn some more background.

+4. Get open-source library six.py from https://pypi.python.org/pypi/six/ and add
+   it to protobuf/third_party/six/six.py.
+5. Apply patches in patches/ (see the description below):
 
-A protobuf.gyp file has been added for building with Chromium.
+   $ for patch in patches/*; do patch -s -p1 < $patch; done
 
-This code has been patched to support unknown field retention in protobuf-lite.
-See r62331 for the patch.
+   For future releases, it will be worth looking into which patches still need
+   to be applied.
+5. Generate descriptor_pb2.py using something like the following steps. Make
+   sure you've regenerated your buildfiles and will build protoc from the
+   newly-modified sources above.
 
-This code has been patched to ensure that files in the target protobuf_lite
-do not include headers from protobuf_full. See r173228 for the patch.
+   $ cd $SRC_DIR
+   $ ninja -C out/Debug protoc
+   $ cd third_party/protobuf/src
+   $ ../../../out/Debug/protoc --python_out=../python google/protobuf/descriptor.proto
 
-This code has been patched to make the target protobuf_lite a component so that
-targets that depend on it can be componentized. See http://crbug.com/172800 for
-details, and r179806 for the patch.
+   Copy the resulting descriptor_pb2.py to protobuf/.

[Peter Kasting, 2016/04/13 02:11:44]

This line is inaccurate and should simply be removed.

[xyzzyz, 2016/04/14 00:23:56]

Done.

+6. Copy __init__.py to protobuf/ (it adds third_party/six/ to Python path).

[Peter Kasting, 2016/04/13 02:11:44]

Copy it from where?

[xyzzyz, 2016/04/14 00:23:56]

I'm not sure how to best express that one should just copy the one I prepared
and put in third_party/protobuf. PTAL.

+7. Update README.chromium.
 
-Revision 504 was cherry-picked from upstream.
-Revision 512 was cherry-picked from upstream.
-Revision 516 was cherry-picked from upstream.
-Revision 517 was cherry-picked from upstream.
-Revision 522 was cherry-picked from upstream.
-Revision 523 was cherry-picked from upstream.
-Revision 524 was cherry-picked from upstream.
-Revision 573 was cherry-picked from upstream.
-The `&file->options() != NULL &&` was removed from descriptor.cc
-References to `vector` were changed to `std::vector` in extension_set.h
-and unknown_field_set.h
+Description of the patches:
 
-GetEmptyString() and GoogleOnceInit() have been uninlined, for a large savings
-in binary size.
+- 0001-ignore-option-retain-unknown-fields.patch
 
-A BUILD.gn file has been added for building with GN.
+  Previous versions of protobuf in Chromium carried a local patch that retained
+  unknown fields in protobuf_lite mode. It was enabled by setting option
+  retain_unknown_fields = true in .proto file. Now that it is enabled by
+  default, this option is no longer recognized by protobuf, and so I had to
+  patch it so that I don't have to fix all .proto files in Chromium in a single
+  CL.
 
-Cherry-pick pherl changes to make protobuf build on VS2015.
+  I plan to remove those occurences, and then this patch will no longer be
+  necessary.
 
-Cherry-pick c3cb53b (fix "sometimes-uninitialized" warning).
+- 0002-remove-support-for-unnecessary-languages.patch
 
-Cherry-pick https://github.com/google/protobuf/commit/56a90a2081379a5
+  This patch removes support for C#, Ruby, Objective-C, JS and other languages not
+  used in Chromium from protoc, to decrease the package size.
 
-Cherry-pick https://github.com/google/protobuf/commit/69d660b39ceabea
+- 0003-remove-static-initializers.patch
 
-Cherry-pick https://github.com/google/protobuf/commit/a74e912a8be1274
+  This patch removes all static initializers from Chromium. The change in Status
+  class is not completely compatible with upstream, but it's compatible enough
+  to work in Chromium, which doesn't use this functionality yet.

[Peter Kasting, 2016/04/13 02:11:44]

Nit: If we land with this patch, it should refer to the upstream issue where the
correct fix is debated.

+
+- 0004-fix-integer-types-and-shared-library-exports.patch
+
+  This patch makes protobuf int64 to be int64_t (as opposed to long long in
+  upstream), and similarly for other integer types. It also allows exporting
+  protobuf symbols in Linux .so libraries.

[Peter Kasting, 2016/04/13 02:11:44]

Why are the int64_t and componentization changes combined in one patch?  Those
are independent things.

The componentization patch should talk about converting to a component and refer
to http://crrev.com/179806 , since that CL and associated bug provide a lot of
useful context for those changes; see my patch's README.

[xyzzyz, 2016/04/14 00:23:56]

They're in a single patch, because I didn't know how to easily separate it into
two patches, and I didn't think it was really worth spending time on it. 

I'll update the comment to talk about componentization.

[Peter Kasting, 2016/04/15 01:12:59]

Do they actually depend on each other?  I just assumed they touched the same
files, in which case it's easy enough to just make two sequential patches that
will apply in some particular order with the relevant pieces.

The patch is small, so it's probably not a big deal, it's mostly an issue if in
the future e.g. upstream accepts the int64_t changes, in which case part of the
patch will still be needed and part won't.

+
+- 0005-fix-no-threadlocal-on-mac.patch
+
+  Apple's Clang doesn't support thread-local variables on Mac.
+
+- 0006-fix-clang-type-errors.patch
+
+  New versions of Clang have type checking semantics that check the conformance
+  with the C++ standard more thorougly, which makes them a bit more
+  restrictive. This is actually cherry-pick from protobuf upstream.

[Peter Kasting, 2016/04/13 02:11:44]

If you've cherry-picked, say exactly which revision you cherry-picked.

[xyzzyz, 2016/04/14 00:23:56]

Done.

+
+- 0007-uninline_googleonce.patch
+- 0008-uninline_get_empty_string.patch
+- 0009-uninline-arenastring.patch
+- 0010-uninline-generated-code.patch
+
+  These patches uninline some functions, resulting in a significant reduction
+  (somewhere between 500 KB and 1 MB) of binary size.