Add UMA protocol buffers to Chrome.

chrome/common/metrics/proto/chrome_user_metrics_extension.proto

Index: chrome/common/metrics/proto/chrome_user_metrics_extension.proto
diff --git a/chrome/common/metrics/proto/chrome_user_metrics_extension.proto b/chrome/common/metrics/proto/chrome_user_metrics_extension.proto
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+// Copyright (c) 2012 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+//
+// Protocol buffer for Chrome UMA (User Metrics Analysis).
+
+syntax = "proto2";
+
+option optimize_for = LITE_RUNTIME;
+
+package metrics;
+
+import "histogram_event.proto";
+import "omnibox_event.proto";
+import "system_profile.proto";
+import "user_action_event.proto";
+
+// Next tag: 7
+message ChromeUserMetricsExtension {
+  // The id of the browser installation that generated these events.
+  // Technically, this id is unique to a top-level (one level above the
+  // "Default" directory) Chrome user data directory [1], and so is shared among
+  // all Chrome user profiles contained in this user data directory.
+  // A UserID of 0 is reserved for test data (monitoring and internal testing)
+  // and should normally be ignored in analysis of the data.
+  // [1] http://www.chromium.org/user-experience/user-data-directory
+  optional fixed64 user_id = 1;
+
+  // The session id for this user.
+  // Values such as tab ids are only meaningful within a particular session.
+  // The client keeps track of the session id and sends it with each event.
+  // The session id is simply an integer that is incremented each time the user
+  // relaunches Chrome.
+  optional int32 session_id = 2;
+
+  // Information about the user's browser and system configuration.
+  optional SystemProfileProto system_profile = 3;
+
+  // This message will log one or more of the following event types:
+  repeated UserActionEventProto user_action_event = 4;
+  repeated OmniboxEventProto omnibox_event = 5;
+  repeated HistogramEventProto histogram_event = 6;
+}