dart2dart: Implementation of simple try/catch.

pkg/compiler/lib/src/tree_ir/optimization/copy_propagator.dart

Index: pkg/compiler/lib/src/tree_ir/optimization/copy_propagator.dart
diff --git a/pkg/compiler/lib/src/tree_ir/optimization/copy_propagator.dart b/pkg/compiler/lib/src/tree_ir/optimization/copy_propagator.dart
index a2828b697d175d31114ec71987939288743b0405..5ab45278bcac6f38cb4d657c9dbc826e0c9235ca 100644
--- a/pkg/compiler/lib/src/tree_ir/optimization/copy_propagator.dart
+++ b/pkg/compiler/lib/src/tree_ir/optimization/copy_propagator.dart
@@ -210,6 +210,12 @@ class CopyPropagator extends RecursiveVisitor with PassMixin {
     throw "WhileCondition before LoopRewriter";
   }
 
+  Statement visitTry(Try node) {
+    node.tryBody = visitBasicBlock(node.tryBody);
+    node.catchBody = visitBasicBlock(node.catchBody);
+    return node;
+  }
+
   Statement visitFunctionDeclaration(FunctionDeclaration node) {
     // Unlike var declarations, function declarations are not hoisted, so we
     // can't do copy propagation of the variable.