dart2js cps: Track existence of try statements in resolution instead of traversing AST/IR nodes to …

pkg/compiler/lib/src/resolution/tree_elements.dart

Index: pkg/compiler/lib/src/resolution/tree_elements.dart
diff --git a/pkg/compiler/lib/src/resolution/tree_elements.dart b/pkg/compiler/lib/src/resolution/tree_elements.dart
index f69e8c2d3ac8ce703c6b28531020d751005b8b5f..3fed5c391a443d4f9ca6872cb519cae5c4153786 100644
--- a/pkg/compiler/lib/src/resolution/tree_elements.dart
+++ b/pkg/compiler/lib/src/resolution/tree_elements.dart
@@ -122,6 +122,9 @@ abstract class TreeElements {
 
   /// Returns the label that [node] targets.
   LabelDefinition getTargetLabel(GotoStatement node);
+
+  /// `true` if the [analyzedElement]'s source code contains a [TryStatement].
+  bool get containsTryStatement;
 }
 
 class TreeElementMapping extends TreeElements {
@@ -140,6 +143,7 @@ class TreeElementMapping extends TreeElements {
   Setlet<Send> _asserts;
   Maplet<Send, SendStructure> _sendStructureMap;
   Setlet<DartType> _requiredTypes;
+  bool containsTryStatement = false;
 
   /// Map from nodes to the targets they define.
   Map<Node, JumpTarget> _definedTargets;