Fix help and error messages.

tools/gn/parse_tree.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/parse_tree.h"
 
 #include <string>
 
 #include "base/stl_util.h"
 #include "base/strings/string_number_conversions.h"
@@ skipping 175 matching lines @@
     statements_[i]->Print(out, indent + 1);
 }
 
 Value BlockNode::ExecuteBlockInScope(Scope* our_scope, Err* err) const {
   for (size_t i = 0; i < statements_.size() && !err->has_error(); i++) {
     // Check for trying to execute things with no side effects in a block.
     const ParseNode* cur = statements_[i];
     if (cur->AsList() || cur->AsLiteral() || cur->AsUnaryOp() ||
         cur->AsIdentifier()) {
       *err = cur->MakeErrorDescribing(
-          "This statment has no effect.",
+          "This statement has no effect.",
           "Either delete it or do something with the result.");
       return Value();
     }
     cur->Execute(our_scope, err);
   }
   return Value();
 }
 
 // ConditionNode --------------------------------------------------------------
 
@@ skipping 254 matching lines @@
 
 Err UnaryOpNode::MakeErrorDescribing(const std::string& msg,
                                      const std::string& help) const {
   return Err(op_, msg, help);
 }
 
 void UnaryOpNode::Print(std::ostream& out, int indent) const {
   out << IndentFor(indent) << "UNARY(" << op_.value() << ")\n";
   operand_->Print(out, indent + 1);
 }