Bound the impact of system instability on chrome instability.

components/browser_watcher/stability_report.proto

Index: components/browser_watcher/stability_report.proto
diff --git a/components/browser_watcher/stability_report.proto b/components/browser_watcher/stability_report.proto
index b5039a23e83b4835b100fae1ab813792daa4ad83..8f028ec5b827b1f3ec199c208d5a2b9cd2a0f4b7 100644
--- a/components/browser_watcher/stability_report.proto
+++ b/components/browser_watcher/stability_report.proto
@@ -10,9 +10,16 @@ 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.
+  enum SessionState {
+    UNKNOWN = 0;
+    CLEAN = 1;
+    UNCLEAN = 2;
+  }
+
+  // The state of the system session that contained Chrome's execution.
+  optional SessionState session_state = 1;
 }
 
 // Next id: 10