Revert https://codereview.chromium.org/1291903002 (protobuf roll).

third_party/protobuf/vsprojects/readme.txt

Index: third_party/protobuf/vsprojects/readme.txt
diff --git a/third_party/protobuf/vsprojects/readme.txt b/third_party/protobuf/vsprojects/readme.txt
new file mode 100644
index 0000000000000000000000000000000000000000..288345ad0a8493427d88b2689bb560a34ca70729
--- /dev/null
+++ b/third_party/protobuf/vsprojects/readme.txt
@@ -0,0 +1,114 @@
+This directory contains project files for compiling Protocol Buffers using
+MSVC.  This is not the recommended way to do Protocol Buffer development --
+we prefer to develop under a Unix-like environment -- but it may be more
+accessible to those who primarily work with MSVC.
+
+Compiling and Installing
+========================
+
+1) Open protobuf.sln in Microsoft Visual Studio.
+2) Choose "Debug" or "Release" configuration as desired.*
+3) From the Build menu, choose "Build Solution".  Wait for compiling to finish.
+4) From a command shell, run tests.exe and lite-test.exe and check that all
+   tests pass.
+5) Run extract_includes.bat to copy all the public headers into a separate
+   "include" directory (under the top-level package directory).
+6) Copy the contents of the include directory to wherever you want to put
+   headers.
+7) Copy protoc.exe wherever you put build tools (probably somewhere in your
+   PATH).
+8) Copy libprotobuf.lib, libprotobuf-lite.lib, and libprotoc.lib wherever you
+   put libraries.
+
+* To avoid conflicts between the MSVC debug and release runtime libraries, when
+  compiling a debug build of your application, you may need to link against a
+  debug build of libprotobuf.lib.  Similarly, release builds should link against
+  release libs.
+
+DLLs vs. static linking
+=======================
+
+Static linking is now the default for the Protocol Buffer libraries.  Due to
+issues with Win32's use of a separate heap for each DLL, as well as binary
+compatibility issues between different versions of MSVC's STL library, it is
+recommended that you use static linkage only.  However, it is possible to
+build libprotobuf and libprotoc as DLLs if you really want.  To do this,
+do the following:
+
+  1) Open protobuf.sln in MSVC.
+  2) For each of the projects libprotobuf, libprotobuf-lite, and libprotoc, do
+     the following:
+    2a) Right-click the project and choose "properties".
+    2b) From the side bar, choose "General", under "Configuration Properties".
+    2c) Change the "Configuration Type" to "Dynamic Library (.dll)".
+    2d) From the side bar, choose "Preprocessor", under "C/C++".
+    2e) Add PROTOBUF_USE_DLLS to the list of preprocessor defines.
+  3) When compiling your project, make sure to #define PROTOBUF_USE_DLLS.
+
+When distributing your software to end users, we strongly recommend that you
+do NOT install libprotobuf.dll or libprotoc.dll to any shared location.
+Instead, keep these libraries next to your binaries, in your application's
+own install directory.  C++ makes it very difficult to maintain binary
+compatibility between releases, so it is likely that future versions of these
+libraries will *not* be usable as drop-in replacements.
+
+If your project is itself a DLL intended for use by third-party software, we
+recommend that you do NOT expose protocol buffer objects in your library's
+public interface, and that you statically link protocol buffers into your
+library.
+
+ZLib support
+============
+
+If you want to include GzipInputStream and GzipOutputStream
+(google/protobuf/io/gzip_stream.h) in libprotoc, you will need to do a few
+additional steps:
+
+1) Obtain a copy of the zlib library.  The pre-compiled DLL at zlib.net works.
+2) Make sure zlib's two headers are in your include path and that the .lib file
+   is in your library path.  You could place all three files directly into the
+   vsproject directory to compile libprotobuf, but they need to be visible to
+   your own project as well, so you should probably just put them into the
+   VC shared icnlude and library directories.
+3) Right-click on the "tests" project and choose "properties".  Navigate the
+   sidebar to "Configuration Properties" -> "Linker" -> "Input".
+4) Under "Additional Dependencies", add the name of the zlib .lib file (e.g.
+   zdll.lib).  Make sure to update both the Debug and Release configurations.
+5) If you are compiling libprotobuf and libprotoc as DLLs (see previous
+   section), repeat steps 2 and 3 for the libprotobuf and libprotoc projects.
+   If you are compiling them as static libraries, then you will need to link
+   against the zlib library directly from your own app.
+6) Edit config.h (in the vsprojects directory) and un-comment the line that
+   #defines HAVE_ZLIB.  (Or, alternatively, define this macro via the project
+   settings.)
+
+Notes on Compiler Warnings
+==========================
+
+The following warnings have been disabled while building the protobuf libraries
+and compiler.  You may have to disable some of them in your own project as
+well, or live with them.
+
+C4018 - 'expression' : signed/unsigned mismatch
+C4146 - unary minus operator applied to unsigned type, result still unsigned
+C4244 - Conversion from 'type1' to 'type2', possible loss of data.
+C4251 - 'identifier' : class 'type' needs to have dll-interface to be used by
+        clients of class 'type2'
+C4267 - Conversion from 'size_t' to 'type', possible loss of data.
+C4305 - 'identifier' : truncation from 'type1' to 'type2'
+C4355 - 'this' : used in base member initializer list
+C4800 - 'type' : forcing value to bool 'true' or 'false' (performance warning)
+C4996 - 'function': was declared deprecated
+
+C4251 is of particular note, if you are compiling the Protocol Buffer library
+as a DLL (see previous section).  The protocol buffer library uses templates in
+its public interfaces.  MSVC does not provide any reasonable way to export
+template classes from a DLL.  However, in practice, it appears that exporting
+templates is not necessary anyway.  Since the complete definition of any
+template is available in the header files, anyone importing the DLL will just
+end up compiling instances of the templates into their own binary.  The
+Protocol Buffer implementation does not rely on static template members being
+unique, so there should be no problem with this, but MSVC prints warning
+nevertheless.  So, we disable it.  Unfortunately, this warning will also be
+produced when compiling code which merely uses protocol buffers, meaning you
+may have to disable it in your code too.