Added framework for generating/consuming benchmarking data sets.

This takes the code that was sitting in benchmarks/
already and makes it easier for language-specific
benchmarks to consume.  Future PRs will enhance this
so that the language-specific benchmarks can report
metrics back that will be tracked over time in PerfKit.
diff --git a/benchmarks/benchmarks.proto b/benchmarks/benchmarks.proto
new file mode 100644
index 0000000..a891eb9
--- /dev/null
+++ b/benchmarks/benchmarks.proto
@@ -0,0 +1,102 @@
+// Protocol Buffers - Google's data interchange format
+// Copyright 2008 Google Inc.  All rights reserved.
+// https://developers.google.com/protocol-buffers/
+//
+// Redistribution and use in source and binary forms, with or without
+// modification, are permitted provided that the following conditions are
+// met:
+//
+//     * Redistributions of source code must retain the above copyright
+// notice, this list of conditions and the following disclaimer.
+//     * Redistributions in binary form must reproduce the above
+// copyright notice, this list of conditions and the following disclaimer
+// in the documentation and/or other materials provided with the
+// distribution.
+//     * Neither the name of Google Inc. nor the names of its
+// contributors may be used to endorse or promote products derived from
+// this software without specific prior written permission.
+//
+// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+
+syntax = "proto3";
+package benchmarks;
+option java_package = "com.google.protobuf.benchmarks";
+
+message BenchmarkDataset {
+  // Name of the benchmark dataset.  This should be unique across all datasets.
+  // Should only contain word characters: [a-zA-Z0-9_]
+  string name = 1;
+
+  // Fully-qualified name of the protobuf message for this dataset.
+  // It will be one of the messages defined benchmark_messages.proto.
+  // Implementations that do not support reflection can implement this with
+  // an explicit "if/else" chain that lists every possible message defined
+  // in this file.
+  string message_name = 2;
+
+  // The payload(s) for this dataset.  They should be parsed or serialized
+  // in sequence, in a loop, ie.
+  //
+  //  while (!benchmarkDone) {  // Benchmark runner decides when to exit.
+  //    for (i = 0; i < benchmark.payload.length; i++) {
+  //      parse(benchmark.payload[i])
+  //    }
+  //  }
+  //
+  // This is intended to let datasets include a variety of data to provide
+  // potentially more realistic results than just parsing the same message
+  // over and over.  A single message parsed repeatedly could yield unusually
+  // good branch prediction performance.
+  repeated bytes payload = 3;
+}
+
+// A benchmark can write out metrics that we will then upload to our metrics
+// database for tracking over time.
+message Metric {
+  // A unique ID for these results.  Used for de-duping.
+  string guid = 1;
+
+  // The tags specify exactly what benchmark was run against the dataset.
+  // The specific benchmark suite can decide what these mean, but here are
+  // some common tags that have a predefined meaning:
+  //
+  //   - "dataset": for tests that pertain to a specific dataset.
+  //
+  // For example:
+  //
+  //   # Tests parsing from binary proto string using arenas.
+  //   tags={
+  //     dataset: "testalltypes",
+  //     op: "parse",
+  //     format: "binaryproto",
+  //     input: "string"
+  //     arena: "true"
+  //   }
+  //
+  //   # Tests serializing to JSON string.
+  //   tags={
+  //     dataset: "testalltypes",
+  //     op: "serialize",
+  //     format: "json",
+  //     input: "string"
+  //   }
+  map<string, string> labels = 2;
+
+  // Unit of measurement for the metric:
+  //  - a speed test might be "mb_per_second" or "ops_per_second"
+  //  - a size test might be "kb".
+  string unit = 3;
+
+  // Metric value.
+  double value = 4;
+}