Fix static analysis warnings in Observatory

runtime/observatory/lib/src/elements/script_inset.dart

Index: runtime/observatory/lib/src/elements/script_inset.dart
diff --git a/runtime/observatory/lib/src/elements/script_inset.dart b/runtime/observatory/lib/src/elements/script_inset.dart
index 2269c12bf9a03851c3f54a5419bc0b6f6a652512..958c777fbf2eaea13c0cebba4880a07bbd450a16 100644
--- a/runtime/observatory/lib/src/elements/script_inset.dart
+++ b/runtime/observatory/lib/src/elements/script_inset.dart
@@ -126,11 +126,8 @@ class BreakpointAnnotation extends Annotation {
       line = script.tokenToLine(pos);
       columnStart = script.tokenToCol(pos) - 1;  // tokenToCol is 1-origin.
     } else {
-      line = bpt.location.line;
-      columnStart = bpt.location.column;
-      if (columnStart == null) {
-        columnStart = 0;
-      }

[turnidge, 2015/09/15 16:01:03]

bpt.location can have two types: SourceLocation and UnresolvedSourceLocation. 
If you remove this code, you will break breakpoint annotations for some
unresolved breakpoints, I think.

[Cutch, 2015/09/15 17:29:57]

Yep, you are right. I've fixed the static warnings in a different way. PTAL.

+      line = 0;
+      columnStart = 0;
     }
     var length = script.guessTokenLength(line, columnStart);
     if (length == null) {
@@ -1019,4 +1016,3 @@ class SourceInsetElement extends PolymerElement {
   @published bool inDebuggerContext = false;
   @published ObservableList variables;
 }
-