Fix crash in assembler when tracing function (must be zone handle). Fixes bug 1709.

runtime/vm/code_generator_ia32.cc

 // 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.
 
 #include "vm/globals.h"  // Needed here to get TARGET_ARCH_IA32.
 #if defined(TARGET_ARCH_IA32)
 
 #include "vm/code_generator.h"
 
 #include "lib/error.h"
@@ skipping 685 matching lines @@
       // EBP + 4 : points to return address.
       // EBP + 8 : address of last argument (arg n-1).
       // ESP + 8 + 4*(n-1) : address of first argument (arg 0).
       // ECX : ic-data array.
       // EDX : arguments descriptor array.
       __ call(&StubCode::CallNoSuchMethodFunctionLabel());
     }
 
     if (FLAG_trace_functions) {
       __ pushl(EAX);  // Preserve result.
-      __ PushObject(function);
+      __ PushObject(Function::ZoneHandle(function.raw()));
       GenerateCallRuntime(AstNode::kNoId,
                           0,
                           kTraceFunctionExitRuntimeEntry);
       __ popl(EAX);  // Remove argument.
       __ popl(EAX);  // Restore result.
     }
     __ LeaveFrame();
     __ ret();
 
     __ Bind(&all_arguments_processed);
@@ skipping 2091 matching lines @@
   const Error& error = Error::Handle(
       Parser::FormatError(script, token_index, "Error", format, args));
   va_end(args);
   Isolate::Current()->long_jump_base()->Jump(1, error);
   UNREACHABLE();
 }
 
 }  // namespace dart
 
 #endif  // defined TARGET_ARCH_IA32