Add 'break' and 'clear' commands to Observatory debugger.

Add 'break' and	'clear' commands to Observatory	debugger.

break adds a breakpoint, clear removes it.

Formats:
  break                   - break at current position
  break 13                - break at line 13, current script
  break	13:20 	          - break at line 13, col 20, current script
  break	script.dart:13    - break at line 13, script.dart
  break	script.dart:13:20 - break at line 13, col 20, script.dart
  break	main              - break at function
  break	FormatException   - break at constructor
  break	_SHA1._updateHash - break at method

clear supports the same location specifiers.

TAB completion works for all of these formats.

The protocol does not yet support setting column-specific or
function/constructor/method breakpoints.  For now we just support
parsing these formats.

Committed: https://code.google.com/p/dart/source/detail?r=43733

[turnidge, 2015-02-11 23:39:06]

turnidge@google.com changed reviewers:
+ johnmccutchan@google.com

[Cutch, 2015-02-12 00:53:26]

LGTMwC

https://codereview.chromium.org/918003002/diff/20001/runtime/observatory/lib/...
File runtime/observatory/lib/src/debugger/source_location.dart (right):

https://codereview.chromium.org/918003002/diff/20001/runtime/observatory/lib/...
runtime/observatory/lib/src/debugger/source_location.dart:26: static
Future<SourceLocation> parse(Debugger debugger, String locDesc) {
It would be really nice to see some unit tests against SourceLocation.parse().

https://codereview.chromium.org/918003002/diff/20001/runtime/observatory/lib/...
runtime/observatory/lib/src/debugger/source_location.dart:72: var line =
int.parse(lineStr, radix:10, onError:(_) => -1);
radix defaults to 10.

[turnidge, 2015-02-12 18:48:26]

https://codereview.chromium.org/918003002/diff/20001/runtime/observatory/lib/...
File runtime/observatory/lib/src/debugger/source_location.dart (right):

https://codereview.chromium.org/918003002/diff/20001/runtime/observatory/lib/...
runtime/observatory/lib/src/debugger/source_location.dart:26: static
Future<SourceLocation> parse(Debugger debugger, String locDesc) {
On 2015/02/12 00:53:25, Cutch wrote:
> It would be really nice to see some unit tests against SourceLocation.parse().

Done.

https://codereview.chromium.org/918003002/diff/20001/runtime/observatory/lib/...
runtime/observatory/lib/src/debugger/source_location.dart:72: var line =
int.parse(lineStr, radix:10, onError:(_) => -1);
On 2015/02/12 00:53:25, Cutch wrote:
> radix defaults to 10.

Fixed.

[turnidge, 2015-02-12 18:49:20]

Committed patchset #3 (id:40001) manually as 43733 (presubmit successful).