Fix linux build.

runtime/vm/debugger.cc

 // Copyright (c) 2011, 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/debugger.h"
 
 #include "vm/code_patcher.h"
 #include "vm/compiler.h"
 #include "vm/flags.h"
 #include "vm/globals.h"
@@ skipping 135 matching lines @@
   }
   initialized_ = true;
   if (!FLAG_debugger) {
     return;
   }
   if (FLAG_bpt == NULL) {
     FLAG_bpt = "main";
   }
   String& cname = String::Handle();
   String& fname = String::Handle();
-  char* dot = strchr(FLAG_bpt, '.');
+  const char* dot = strchr(FLAG_bpt, '.');
   if (dot == NULL) {
     fname = String::New(FLAG_bpt);
   } else {
     fname = String::New(dot + 1);
     cname = String::New(reinterpret_cast<const uint8_t*>(FLAG_bpt),
                         dot - FLAG_bpt);
   }
   SetBreakpointAtEntry(cname, fname);
 }
 
@@ skipping 11 matching lines @@
 
 
 void Debugger::AddBreakpoint(Breakpoint* bpt) {
   ASSERT(bpt->next() == NULL);
   bpt->set_next(this->breakpoints_);
   this->breakpoints_ = bpt;
 }
 
 
 }  // namespace dart