Move HandlerList to shared ExceptionHandlerList.

runtime/vm/code_generator_x64.h

Index: runtime/vm/code_generator_x64.h
===================================================================
--- runtime/vm/code_generator_x64.h	(revision 6234)
+++ runtime/vm/code_generator_x64.h	(working copy)
@@ -21,6 +21,7 @@
 class AstNode;
 class CodeGenerator;
 class DescriptorList;
+class ExceptionHandlerList;
 class SourceLabel;
 class StackmapBuilder;
 
@@ -119,9 +120,6 @@
   // structured.
   friend class OptimizingCodeGenerator;
 
-  // Forward declarations.
-  class HandlerList;
-
   // Return true if intrinsification was completed and no other code
   // needs to be generated.
   virtual bool TryIntrinsify() { return false; }
@@ -216,7 +214,7 @@
   CodeGeneratorState* state_;
   DescriptorList* pc_descriptors_list_;
   StackmapBuilder* stackmap_builder_;
-  HandlerList* exception_handlers_list_;
+  ExceptionHandlerList* exception_handlers_list_;
   int try_index_;
   // The runtime context level is only incremented when a new context is
   // allocated and chained to the list of contexts.