Revive throw as an expression but not for rethrow.

sdk/lib/_internal/compiler/implementation/scanner/listener.dart

Index: sdk/lib/_internal/compiler/implementation/scanner/listener.dart
===================================================================
--- sdk/lib/_internal/compiler/implementation/scanner/listener.dart	(revision 15894)
+++ sdk/lib/_internal/compiler/implementation/scanner/listener.dart	(working copy)
@@ -319,13 +319,13 @@
   void endSwitchBlock(int caseCount, Token beginToken, Token endToken) {
   }
 
-  void beginThrowStatement(Token token) {
+  void beginThrow(Token token) {
   }
 
-  void endThrowStatement(Token throwToken, Token endToken) {
+  void endThrow(Token throwToken, Token endToken) {
   }
 
-  void endRethrowStatement(Token throwToken, Token endToken) {
+  void endRethrow(Token throwToken, Token endToken) {
   }
 
   void beginTopLevelMember(Token token) {
@@ -1481,12 +1481,12 @@
     pushNode(new Block(makeNodeList(count, beginToken, endToken, null)));
   }
 
-  void endThrowStatement(Token throwToken, Token endToken) {
+  void endThrow(Token throwToken, Token endToken) {
     Expression expression = popNode();
     pushNode(new Throw(expression, throwToken, endToken));
   }
 
-  void endRethrowStatement(Token throwToken, Token endToken) {
+  void endRethrow(Token throwToken, Token endToken) {
     pushNode(new Throw(null, throwToken, endToken));
   }