headless: Add a headless shell

BUILD.gn

 # 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.
 
 # This is the root build file for GN. GN will start processing by loading this
 # file, and recursively load all dependencies until all dependencies are either
 # resolved or known not to exist (which will cause the build to fail). So if
 # you add a new build file, there must be some path of dependencies from this
 # file to your new one or GN won't know about it.
 
@@ skipping 628 matching lines @@
   }
 
   if (is_android) {
     deps += [ "//blimp" ]
   }
 
   if (is_mac) {
     deps -= [ "//mandoline:all" ]  # TODO(GYP)
   }
 
+  if (is_headless) {

[Peter Beverloo, 2015/10/27 14:35:51]

Does this need to be defined somewhere?

Documenting it in //tools/gn/docs/cookbook.md also seems appropriate.

+    deps += [ "//headless" ]
+  }
+
   if (use_libfuzzer) {
     deps += [ "//testing/libfuzzer:libfuzzer_main" ]
   }
 }
 
 group("gn_mojo_targets") {
   testonly = true
   if (is_linux && !is_chromeos) {
     # TODO(GYP): Figure out if any of these should be in gn_all
     # and figure out how cross-platform they are
@@ skipping 120 matching lines @@
       if (target_cpu == "x86") {
         deps += [
           # "//content/shell:crash_service_win64", TODO(GYP): crbug.com/537009
         ]
       }
     } else {
       deps += [ "//breakpad:minidump_stackwalk($host_toolchain)" ]
     }
   }
 }