Issue 5359. Highlight 'on' in try-catch statement.

compiler/java/com/google/dart/compiler/ast/DartCatchBlock.java

 // 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.
 
 package com.google.dart.compiler.ast;
 
 /**
  * Represents a Dart 'catch' block.
  */
 public class DartCatchBlock extends DartStatement {
-  private DartParameter exception;
-  private DartParameter stackTrace;
-  private DartBlock block;
+  private final int onTokenOffset;
+  private final DartParameter exception;
+  private final DartParameter stackTrace;
+  private final DartBlock block;
 
   public DartCatchBlock(DartBlock block,
+                        int onTokenOffset,
                         DartParameter exception,
                         DartParameter stackTrace) {
     this.block = becomeParentOf(block);
+    this.onTokenOffset = onTokenOffset;
     this.exception = becomeParentOf(exception);
     this.stackTrace = becomeParentOf(stackTrace);
   }
 
+  public int getOnTokenOffset() {
+    return onTokenOffset;
+  }
+
   public DartParameter getException() {
     return exception;
   }
 
   public DartParameter getStackTrace() {
     return stackTrace;
   }
 
   public DartBlock getBlock() {
     return block;
   }
 
   @Override
   public void visitChildren(ASTVisitor<?> visitor) {
     safelyVisitChild(exception, visitor);
     safelyVisitChild(stackTrace, visitor);
     safelyVisitChild(block, visitor);
   }
 
   @Override
   public <R> R accept(ASTVisitor<R> visitor) {
     return visitor.visitCatchBlock(this);
   }
 }