Added 3.0.0-beta-4 changelog.

Change-Id: I997012e7e9b58d9ec8b2f59429d71c98d81aa40d

CHANGES.txt

@@ -1,3 +1,83 @@
+2016-07-15 version 3.0.0-beta-4 (C++/Java/Python/Ruby/Objective-C/C#/JavaScript)
+  General
+  * Added a deterministic serialization API for C++ and Java. The deterministic
+    serialization guarantees that given a binary, equal messages will be
+    serialized to the same bytes. This allows applications like MapReduce to
+    group equal messages based on the serialized bytes. The deterministic
+    serialization is, however, NOT canonical across languages; it is also
+    unstable across different builds with schema changes due to unknown fields.
+    Users who need canonical serialization, e.g. persistent storage in a
+    canonical form, fingerprinting, etc, should define their own
+    canonicalization specification and implement the serializer using reflection
+    APIs rather than relying on this API.
+  * Added OneofOptions. You can now define custom options for oneof groups.
+      import "google/protobuf/descriptor.proto";
+      extend google.protobuf.OneofOptions {
+        optional int32 my_oneof_extension = 12345;
+      }
+      message Foo {
+        oneof oneof_group {
+          (my_oneof_extension) = 54321;
+          ...
+        }
+      }
+
+  C++ (beta)
+  * Introduced a deterministic serialization API in
+    CodedOutputStream::SetSerializationDeterministic(bool). See the notes about
+    deterministic serialization in the General section.
+  * Added google::protobuf::Map::swap() to swap two map fields.
+  * Fixed a memory leak when calling Reflection::ReleaseMessage() on a message
+    allocated on arena.
+  * Improved error reporting when parsing text format protos.
+  * JSON
+      - Added a new parser option to ignore unknown fields when parsing JSON.
+      - Added convenient methods for message to/from JSON conversion.
+  * Various performance optimizations.
+
+  Java (beta)
+  * Introduced a deterministic serialization API in
+    CodedOutputStream#useDeterministicSerialization(). See the notes about
+    deterministic serialization in the General section.
+  * File option "java_generate_equals_and_hash" is now deprecated. equals() and
+    hashCode() methods are generated by default.
+  * Added a new JSON printer option "omittingInsignificantWhitespace" to produce
+    a more compact JSON output. The printer will pretty-print by default.
+  * Updated Java runtime to be compatible with 2.5.0/2.6.1 generated protos.
+
+  Python (beta)
+  * Added support to pretty print Any messages in text format.
+  * Added a flag to ignore unknown fields when parsing JSON.
+  * Bugfix: "@type" field of a JSON Any message is now correctly put before
+    other fields.
+
+  Objective-C (beta)
+  * Updated the code to support compiling with more compiler warnings
+    enabled. (Issue 1616)
+  * Exposing more detailed errors for parsing failures. (PR 1623)
+  * Small (breaking) change to the naming of some methods on the support classes
+    for map<>. There were collisions with the system provided KVO support, so
+    the names were changed to avoid those issues.  (PR 1699)
+  * Fixed for proper Swift bridging of error handling during parsing. (PR 1712)
+  * Complete support for generating sources that will go into a Framework and
+    depend on generated sources from other Frameworks. (Issue 1457)
+
+  C# (beta)
+  * RepeatedField optimizations.
+  * Support for .NET Core.
+  * Minor bug fixes.
+  * Ability to format a single value in JsonFormatter (advanced usage only).
+  * Modifications to attributes applied to generated code.
+
+  Javascript (alpha)
+  * Maps now have a real map API instead of being treated as repeated fields.
+  * Well-known types are now provided in the google-protobuf package, and the
+    code generator knows to require() them from that package.
+  * Bugfix: non-canonical varints are correctly decoded.
+
+  Ruby (alpha)
+  * Accessors for oneof fields now return default values instead of nil.
+
 2016-05-16 version 3.0.0-beta-3 (C++/Java/Python/Ruby/Nano/Objective-C/C#/JavaScript)
   General
   * Supported Proto3 lite-runtime in C++/Java for mobile platforms.