Fix help and error messages.

tools/gn/builder.cc

 // Copyright (c) 2013 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "tools/gn/builder.h"
 
 #include "tools/gn/config.h"
 #include "tools/gn/err.h"
 #include "tools/gn/loader.h"
 #include "tools/gn/scheduler.h"
@@ skipping 261 matching lines @@
 }
 
 BuilderRecord* Builder::GetResolvedRecordOfType(const Label& label,
                                                 const ParseNode* origin,
                                                 BuilderRecord::ItemType type,
                                                 Err* err) {
   BuilderRecord* record = GetRecord(label);
   if (!record) {
     *err = Err(origin, "Item not found",
         "\"" + label.GetUserVisibleName(false) + "\" doesn't\n"
-        "refer to an existant thing.");
+        "refer to an existent thing.");
     return NULL;
   }
 
   const Item* item = record->item();
   if (!item) {
     *err = Err(origin, "Item not resolved.",
         "\"" + label.GetUserVisibleName(false) + "\" hasn't been resolved.\n");
     return NULL;
   }
 
@@ skipping 169 matching lines @@
   // Walk backwards since the dependency arrows point in the reverse direction.
   std::string ret;
   for (int i = static_cast<int>(cycle.size()) - 1; i >= 0; i--) {
     ret += "  " + cycle[i]->label().GetUserVisibleName(false);
     if (i != 0)
       ret += " ->\n";
   }
 
   return ret;
 }