Bound the impact of system instability on chrome instability.

components/browser_watcher/stability_report.proto

 // Copyright 2016 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.
 
 syntax = "proto2";
 
 option optimize_for = LITE_RUNTIME;
 
 package browser_watcher;
 
 // The state of the system on which Chrome is running (shutting down, battery
 // level, load, etc.).
-// Next id: 1
+// Next id: 2
 message SystemState {
-  // TODO(manzagop): flesh out.
+  // The state of a system session. A system session begins when the system
+  // starts and ends when it shuts down.
+  enum SessionState {
+    UNKNOWN = 0;
+    CLEAN = 1;    // Normal shutdown.
+    UNCLEAN = 2;  // Abnormal shutdown (system crash, power loss).
+  }
+
+  // The state of the system session that contained Chrome's execution.
+  optional SessionState session_state = 1;
 }
 
 // Next id: 10
 message CodeModule {
   // The base address of this code module as it was loaded by the process.
   optional int64 base_address = 1;
 
   // The size of the code module.
   optional int64 size = 2;
 
@@ skipping 151 matching lines @@
   //     command line, etc.
   repeated ProcessState process_states = 2;
   // TODO(manzagop): if/when reports contain multiple processes, attribute and
   //     relocate these to their process (and perhaps thread).
   repeated string log_messages = 3;
   map<string, TypedValue> global_data = 4;
 
   // The field trials the user is currently enrolled in.
   repeated FieldTrial field_trials = 5;
 }