Capture more data when instrumenting exceptions

pkg/analyzer/lib/instrumentation/instrumentation.dart

Index: pkg/analyzer/lib/instrumentation/instrumentation.dart
diff --git a/pkg/analyzer/lib/instrumentation/instrumentation.dart b/pkg/analyzer/lib/instrumentation/instrumentation.dart
index ee3c74729ea2474cef10fafe2f742dc9eea56fb0..40db35e549652c429e6dac3b240f6d868c1ce9d9 100644
--- a/pkg/analyzer/lib/instrumentation/instrumentation.dart
+++ b/pkg/analyzer/lib/instrumentation/instrumentation.dart
@@ -150,12 +150,14 @@ class InstrumentationService {
    * entry has the given [level] and [message], and was created at the given
    * [time].
    */
-  void logLogEntry(String level, DateTime time, String message) {
+  void logLogEntry(String level, DateTime time, String message, Object exception, StackTrace stackTrace) {

[lukechurch, 2015/08/03 13:36:14]

This feels a bit strange to me - why are the exception and stacktrace mandatory
objects rather than optional parameters?

Given that the implementation is not safe if exception or stackTrace are null -
they really do need to be instances. What is the expectation of what they will
hold in non-error conditions?

Is this a standard pattern from the logging library?

[Brian Wilkerson, 2015/08/03 14:07:40]

This is only called from the logger, and it didn't seem worth making them
optional. Also, there's no way to express that they should either both be given
or both be absent, so the semantics would be equally strange if they were
optional.
I'm not sure why you say that. "null.toString()" is perfectly valid and produces
"null", which is what we'll send to the instrumentation server if they are not
provided.
I assume this is part of the previous question and not a separate question. If I
misunderstood, let me know.

     if (_instrumentationServer != null) {
       String timeStamp =
           time == null ? 'null' : time.millisecondsSinceEpoch.toString();
+      String exceptionText = exception.toString();
+      String stackTraceText = stackTrace.toString();
       _instrumentationServer
-          .log(_join([TAG_LOG_ENTRY, level, timeStamp, message]));
+          .log(_join([TAG_LOG_ENTRY, level, timeStamp, message, exceptionText, stackTraceText]));
     }
   }