Fix some typos in gn's documentation for "copy".

tools/gn/functions_target.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/functions.h"
 
 #include "tools/gn/config_values_generator.h"
 #include "tools/gn/err.h"
 #include "tools/gn/parse_tree.h"
 #include "tools/gn/scope.h"
@@ skipping 234 matching lines @@
 const char kCopy_Help[] =
     "copy: Declare a target that copies files.\n"
     "\n"
     "File name handling\n"
     "\n"
     "  All output files must be inside the output directory of the build.\n"
     "  You would generally use |$target_out_dir| or |$target_gen_dir| to\n"
     "  reference the output or generated intermediate file directories,\n"
     "  respectively.\n"
     "\n"
-    "  Both \"sources\" and \"outputs\" must be specified. Sources can\n"
+    "  Both \"sources\" and \"outputs\" must be specified. Sources can "
+    "include\n"
     "  as many files as you want, but there can only be one item in the\n"
     "  outputs list (plural is used for the name for consistency with\n"
     "  other target types).\n"
     "\n"
     "  If there is more than one source file, your output name should specify\n"
-    "  a mapping from each source files to output file names using source\n"
+    "  a mapping from each source file to an output file name using source\n"
     "  expansion (see \"gn help source_expansion\"). The placeholders will\n"
-    "  will look like \"{{source_name_part}}\", for example.\n"
+    "  look like \"{{source_name_part}}\", for example.\n"
     "\n"
     "Examples\n"
     "\n"
     "  # Write a rule that copies a checked-in DLL to the output directory.\n"
     "  copy(\"mydll\") {\n"
     "    sources = [ \"mydll.dll\" ]\n"
     "    outputs = [ \"$target_out_dir/mydll.dll\" ]\n"
     "  }\n"
     "\n"
     "  # Write a rule to copy several files to the target generated files\n"
@@ skipping 246 matching lines @@
   const Template* templ = scope->GetTemplate(target_type);
   if (templ)
     return templ->Invoke(scope, function, sub_args, block, err);
 
   // Otherwise, assume the target is a built-in target type.
   return ExecuteGenericTarget(target_type.c_str(), scope, function, sub_args,
                               block, err);
 }
 
 }  // namespace functions