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

third_party/protobuf/CHANGES.txt

-2015-05-25 version 3.0.0-alpha-3 (Objective-C/C#):
-  General
-  * Introduced two new language implementations (Objective-C, C#) to proto3.
-  * Explicit "optional" keyword are disallowed in proto3 syntax, as fields are
-    optional by default.
-  * Group fields are no longer supported in proto3 syntax.
-  * Changed repeated primitive fields to use packed serialization by default in
-    proto3 (implemented for C++, Java, Python in this release).  The user can
-    still disable packed serialization by setting packed to false for now.
-  * Added well-known type protos (any.proto, empty.proto, timestamp.proto,
-    duration.proto, etc.). Users can import and use these protos just like
-    regular proto files. Addtional runtime support will be added for them in
-    future releases (in the form of utility helper functions, or having them
-    replaced by language specific types in generated code).
-  * Added a "reserved" keyword in both proto2 and proto3 syntax. User can use
-    this keyword to declare reserved field numbers and names to prevent them
-    from being reused by other fields in the same message.
-
-    To reserve field numbers, add a reserved declaration in your message:
-
-      message TestMessage {
-        reserved 2, 15, 9 to 11, 3;
-      }
-
-    This reserves field numbers 2, 3, 9, 10, 11 and 15. If a user uses any of
-    these as field numbers, the protocol buffer compiler will report an error.
-
-    Field names can also be reserved:
-
-      message TestMessage {
-        reserved "foo", "bar";
-      }
-
-  * Various bug fixes since 3.0.0-alpha-2
-
-  Objective-C
-    Objective-C includes a code generator and a native objective-c runtime
-    library.  By adding “--objc_out” to protoc, the code generator will generate
-    a header(*.pbobjc.h) and an implementation file(*.pbobjc.m) for each proto
-    file.
-
-    In this first release, the generated interface provides: enums, messages,
-    field support(single, repeated, map, oneof), proto2 and proto3 syntax
-    support, parsing and serialization. It’s  compatible with ARC and non-ARC
-    usage. Besides, user can also access it via the swift bridging header.
-
-    See objectivec/README.md for details.
-
-  C#
-    * C# protobufs are based on project
-      https://github.com/jskeet/protobuf-csharp-port. The original project was
-      frozen and all the new development will happen here.
-    * Codegen plugin for C# was completely rewritten to C++ and is now an
-      intergral part of protoc.
-    * Some refactorings and cleanup has been applied to the C# runtime library.
-    * Only proto2 is supported in C# at the moment, proto3 support is in
-      progress and will likely bring significant breaking changes to the API.
-
-    See csharp/README.md for details.
-
-  C++
-    * Added runtime support for Any type. To use Any in your proto file, first
-      import the definition of Any:
-
-        // foo.proto
-        import "google/protobuf/any.proto";
-        message Foo {
-          google.protobuf.Any any_field = 1;
-        }
-        message Bar {
-          int32 value = 1;
-        }
-
-      Then in C++ you can access the Any field using PackFrom()/UnpackTo()
-      methods:
-
-        Foo foo;
-        Bar bar = ...;
-        foo.mutable_any_field()->PackFrom(bar);
-        ...
-        if (foo.any_field().IsType<Bar>()) {
-          foo.any_field().UnpackTo(&bar);
-          ...
-        }
-    * In text format, entries of a map field will be sorted by key.
-
-  Java
-    * Continued optimizations on the lite runtime to improve performance for
-      Android.
-
-  Python
-    * Added map support.
-      - maps now have a dict-like interface (msg.map_field[key] = value)
-      - existing code that modifies maps via the repeated field interface
-        will need to be updated.
-
-  Ruby
-    * Improvements to RepeatedField's emulation of the Ruby Array API.
-    * Various speedups and internal cleanups.
-
-2015-02-26 version 3.0.0-alpha-2 (Python/Ruby/JavaNano):
-  General
-  * Introduced three new language implementations (Ruby, JavaNano, and
-    Python) to proto3.
-  * Various bug fixes since 3.0.0-alpha-1
-
-  Python:
-    Python has received several updates, most notably support for proto3
-    semantics in any .proto file that declares syntax="proto3".
-    Messages declared in proto3 files no longer represent field presence
-    for scalar fields (number, enums, booleans, or strings).  You can
-    no longer call HasField() for such fields, and they are serialized
-    based on whether they have a non-zero/empty/false value.
-
-    One other notable change is in the C++-accelerated implementation.
-    Descriptor objects (which describe the protobuf schema and allow
-    reflection over it) are no longer duplicated between the Python
-    and C++ layers.  The Python descriptors are now simple wrappers
-    around the C++ descriptors.  This change should significantly
-    reduce the memory usage of programs that use a lot of message
-    types.
-
-  Ruby:
-    We have added proto3 support for Ruby via a native C extension.
-
-    The Ruby extension itself is included in the ruby/ directory, and details on
-    building and installing the extension are in ruby/README.md. The extension
-    will also be published as a Ruby gem. Code generator support is included as
-    part of `protoc` with the `--ruby_out` flag.
-
-    The Ruby extension implements a user-friendly DSL to define message types
-    (also generated by the code generator from `.proto` files).  Once a message
-    type is defined, the user may create instances of the message that behave in
-    ways idiomatic to Ruby. For example:
-
-    - Message fields are present as ordinary Ruby properties (getter method
-      `foo` and setter method `foo=`).
-    - Repeated field elements are stored in a container that acts like a native
-      Ruby array, and map elements are stored in a container that acts like a
-      native Ruby hashmap.
-    - The usual well-known methods, such as `#to_s`, `#dup`, and the like, are
-      present.
-
-    Unlike several existing third-party Ruby extensions for protobuf, this
-    extension is built on a "strongly-typed" philosophy: message fields and
-    array/map containers will throw exceptions eagerly when values of the
-    incorrect type are inserted.
-
-    See ruby/README.md for details.
-
-  JavaNano:
-    JavaNano is a special code generator and runtime library designed especially
-    for resource-restricted systems, like Android. It is very resource-friendly
-    in both the amount of code and the runtime overhead. Here is an an overview
-    of JavaNano features compared with the official Java protobuf:
-
-    - No descriptors or message builders.
-    - All messages are mutable; fields are public Java fields.
-    - For optional fields only, encapsulation behind setter/getter/hazzer/
-      clearer functions is opt-in, which provide proper 'has' state support.
-    - For proto2, if not opted in, has state (field presence) is not available.
-      Serialization outputs all fields not equal to their defaults.
-      The behavior is consistent with proto3 semantics.
-    - Required fields (proto2 only) are always serialized.
-    - Enum constants are integers; protection against invalid values only
-      when parsing from the wire.
-    - Enum constants can be generated into container interfaces bearing
-      the enum's name (so the referencing code is in Java style).
-    - CodedInputByteBufferNano can only take byte[] (not InputStream).
-    - Similarly CodedOutputByteBufferNano can only write to byte[].
-    - Repeated fields are in arrays, not ArrayList or Vector. Null array
-      elements are allowed and silently ignored.
-    - Full support for serializing/deserializing repeated packed fields.
-    - Support  extensions (in proto2).
-    - Unset messages/groups are null, not an immutable empty default
-      instance.
-    - toByteArray(...) and mergeFrom(...) are now static functions of
-      MessageNano.
-    - The 'bytes' type translates to the Java type byte[].
-
-    See javanano/README.txt for details.
-
-2014-12-01 version 3.0.0-alpha-1 (C++/Java):
-
-  General
-  * Introduced Protocol Buffers language version 3 (aka proto3).
-
-    When protobuf was initially opensourced it implemented Protocol Buffers
-    language version 2 (aka proto2), which is why the version number
-    started from v2.0.0. From v3.0.0, a new language version (proto3) is
-    introduced while the old version (proto2) will continue to be supported.
-
-    The main intent of introducing proto3 is to clean up protobuf before
-    pushing the language as the foundation of Google's new API platform.
-    In proto3, the language is simplified, both for ease of use and  to
-    make it available in a wider range of programming languages. At the
-    same time a few features are added to better support common idioms
-    found in APIs.
-
-    The following are the main new features in language version 3:
-
-      1. Removal of field presence logic for primitive value fields, removal
-         of required fields, and removal of default values. This makes proto3
-         significantly easier to implement with open struct representations,
-         as in languages like Android Java, Objective C, or Go.
-      2. Removal of unknown fields.
-      3. Removal of extensions, which are instead replaced by a new standard
-         type called Any.
-      4. Fix semantics for unknown enum values.
-      5. Addition of maps.
-      6. Addition of a small set of standard types for representation of time,
-         dynamic data, etc.
-      7. A well-defined encoding in JSON as an alternative to binary proto
-         encoding.
-
-    This release (v3.0.0-alpha-1) includes partial proto3 support for C++ and
-    Java. Items 6 (well-known types) and 7 (JSON format) in the above feature
-    list are not impelmented.
-
-    A new notion "syntax" is introduced to specify whether a .proto file
-    uses proto2 or proto3:
-
-      // foo.proto
-      syntax = "proto3";
-      message Bar {...}
-
-    If omitted, the protocol compiler will generate a warning and "proto2" will
-    be used as the default. This warning will be turned into an error in a
-    future release.
-
-    We recommend that new Protocol Buffers users use proto3. However, we do not
-    generally recommend that existing users migrate from proto2 from proto3 due
-    to API incompatibility, and we will continue to support proto2 for a long
-    time.
-
-  * Added support for map fields (implemented in C++/Java for both proto2 and
-    proto3).
-
-    Map fields can be declared using the following syntax:
-
-      message Foo {
-        map<string, string> values = 1;
-      }
-
-    Data of a map field will be stored in memory as an unordered map and it
-    can be accessed through generated accessors.
-
-  C++
-  * Added arena allocation support (for both proto2 and proto3).
-
-    Profiling shows memory allocation and deallocation constitutes a significant
-    fraction of CPU-time spent in protobuf code and arena allocation is a
-    technique introduced to reduce this cost. With arena allocation, new
-    objects will be allocated from a large piece of preallocated memory and
-    deallocation of these objects is almost free. Early adoption shows 20% to
-    50% improvement in some Google binaries.
-
-    To enable arena support, add the following option to your .proto file:
-
-      option cc_enable_arenas = true;
-
-    Protocol compiler will generate additional code to make the generated
-    message classes work with arenas. This does not change the existing API
-    of protobuf messages and does not affect wire format. Your existing code
-    should continue to work after adding this option. In the future we will
-    make this option enabled by default.
-
-    To actually take advantage of arena allocation, you need to use the arena
-    APIs when creating messages. A quick example of using the arena API:
-
-      {
-        google::protobuf::Arena arena;
-        // Allocate a protobuf message in the arena.
-        MyMessage* message = Arena::CreateMessage<MyMessage>(&arena);
-        // All submessages will be allocated in the same arena.
-        if (!message->ParseFromString(data)) {
-          // Deal with malformed input data.
-        }
-        // Must not delete the message here. It will be deleted automatically
-        // when the arena is destroyed.
-      }
-
-    Currently arena does not work with map fields. Enabling arena in a .proto
-    file containing map fields will result in compile errors in the generated
-    code. This will be addressed in a future release.
-
-2014-10-20 version 2.6.1:
-
-  C++
-  * Added atomicops support for Solaris.
-  * Released memory allocated by InitializeDefaultRepeatedFields() and
-    GetEmptyString(). Some memory sanitizers reported them as memory leaks.
-
-  Java
-  * Updated DynamicMessage.setField() to handle repeated enum values
-    correctly.
-  * Fixed a bug that caused NullPointerException to be thrown when
-    converting manually constructed FileDescriptorProto to
-    FileDescriptor.
-
-  Python
-  * Fixed WhichOneof() to work with de-serialized protobuf messages.
-  * Fixed a missing file problem of Python C++ implementation.
-
-2014-08-15 version 2.6.0:
-
-  General
-  * Added oneofs(unions) feature. Fields in the same oneof will share
-    memory and at most one field can be set at the same time. Use the
-    oneof keyword to define a oneof like:
-      message SampleMessage {
-        oneof test_oneof {
-          string name = 4;
-          YourMessage sub_message = 9;
-        }
-      }
-  * Files, services, enums, messages, methods and enum values can be marked
-    as deprecated now.
-  * Added Support for list values, including lists of mesaages, when
-    parsing text-formatted protos in C++ and Java.
-      For example:  foo: [1, 2, 3]
-
-  C++
-  * Enhanced customization on TestFormat printing.
-  * Added SwapFields() in reflection API to swap a subset of fields.
-    Added SetAllocatedMessage() in reflection API.
-  * Repeated primitive extensions are now packable. The
-    [packed=true] option only affects serializers. Therefore, it is
-    possible to switch a repeated extension field to packed format
-    without breaking backwards-compatibility.
-  * Various speed optimizations.
-
-  Java
-  * writeTo() method in ByteString can now write a substring to an
-    output stream. Added endWith() method for ByteString.
-  * ByteString and ByteBuffer are now supported in CodedInputStream
-    and CodedOutputStream.
-  * java_generate_equals_and_hash can now be used with the LITE_RUNTIME.
-
-  Python
-  * A new C++-backed extension module (aka "cpp api v2") that replaces the
-    old ("cpp api v1") one.  Much faster than the pure Python code.  This one
-    resolves many bugs and is recommended for general use over the
-    pure Python when possible.
-  * Descriptors now have enum_types_by_name and extension_types_by_name dict
-    attributes.
-  * Support for Python 3.
-
-2013-02-27 version 2.5.0:
+2012-09-19 version 2.5.0:
 
   General
   * New notion "import public" that allows a proto file to forward the content
     it imports to its importers. For example,
       // foo.proto
       import public "bar.proto";
       import "baz.proto";
 
       // qux.proto
       import "foo.proto";
       // Stuff defined in bar.proto may be used in this file, but stuff from
       // baz.proto may NOT be used without importing it explicitly.
     This is useful for moving proto files. To move a proto file, just leave
     a single "import public" in the old proto file.
   * New enum option "allow_alias" that specifies whether different symbols can
     be assigned the same numeric value. Default value is "true". Setting it to
     false causes the compiler to reject enum definitions where multiple symbols
     have the same numeric value.
-    Note: We plan to flip the default value to "false" in a future release.
-    Projects using enum aliases should set the option to "true" in their .proto
-    files.
 
   C++
   * New generated method set_allocated_foo(Type* foo) for message and string
     fields. This method allows you to set the field to a pre-allocated object
     and the containing message takes the ownership of that object.
   * Added SetAllocatedExtension() and ReleaseExtension() to extensions API.
   * Custom options are now formatted correctly when descriptors are printed in
     text format.
   * Various speed optimizations.
 
   Java
   * Comments in proto files are now collected and put into generated code as
     comments for corresponding classes and data members.
   * Added Parser to parse directly into messages without a Builder. For
     example,
-      Foo foo = Foo.PARSER.ParseFrom(input);
+      Foo foo = Foo.getParser().ParseFrom(input);
     Using Parser is ~25% faster than using Builder to parse messages.
   * Added getters/setters to access the underlying ByteString of a string field
     directly.
   * ByteString now supports more operations: substring(), prepend(), and
     append(). The implementation of ByteString uses a binary tree structure
     to support these operations efficiently.
   * New method findInitializationErrors() that lists all missing required
     fields.
   * Various code size and speed optimizations.
 
@@ skipping 473 matching lines @@
     contain extra zeros.
   * Fix Python service CallMethod() implementation.
 
   Other
   * Improved readmes.
   * VIM syntax highlighting improvements.
 
 2008-07-07 version 2.0.0:
 
   * First public release.