Improve exception handling:

dart/frog/leg/ssa/codegen.dart

 // Copyright (c) 2012, the Dart project authors.  Please see the AUTHORS file
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
 class SsaCodeGeneratorTask extends CompilerTask {
   SsaCodeGeneratorTask(Compiler compiler) : super(compiler);
   String get name() => 'SSA code generator';
 
   String generate(WorkItem work, HGraph graph) {
     return measure(() {
@@ skipping 426 matching lines @@
     indent--;
 
     if (node.finallyBlock != successors[1]) {
       // Printing the catch part.
       addIndentation();
       String name = temporary(node.exception);
       parameterNames[node.exception.element] = name;
       buffer.add('} catch ($name) {\n');
       indent++;
       addIndentation();
-      buffer.add('$name = $name.dartException;\n');
       visitBasicBlock(successors[1]);
       parameterNames.remove(node.exception.element);
       indent--;
     }
 
     if (node.finallyBlock != null) {
       addIndentation();
       buffer.add('} finally {\n');
       indent++;
       visitBasicBlock(node.finallyBlock);
@@ skipping 252 matching lines @@
       use(node.inputs[0], JSPrecedence.EXPRESSION_PRECEDENCE);
       buffer.add(';\n');
     }
   }
 
   visitThis(HThis node) {
     buffer.add('this');
   }
 
   visitThrow(HThrow node) {
-    generateThrowWithHelper('captureStackTrace', node.inputs[0]);
+    if (node.isRethrow) {
+      buffer.add('throw ');
+      use(node.inputs[0], JSPrecedence.EXPRESSION_PRECEDENCE);
+    } else {
+      generateThrowWithHelper('captureStackTrace', node.inputs[0]);
+    }
     buffer.add(';\n');
   }
 
   visitBoundsCheck(HBoundsCheck node) {
     buffer.add('if (');
     use(node.index, JSPrecedence.RELATIONAL_PRECEDENCE);
     buffer.add(' < 0 || ');
     use(node.index, JSPrecedence.RELATIONAL_PRECEDENCE);
     buffer.add(' >= ');
     use(node.length, JSPrecedence.SHIFT_PRECEDENCE);
@@ skipping 612 matching lines @@
       startBailoutSwitch();
     }
   }
 
   void endElse(HIf node) {
     if (node.elseBlock.hasBailouts()) {
       endBailoutSwitch();
     }
   }
 }