Add a prototype today extension behind gn flag

ios/chrome/app/BUILD.gn

 # Copyright 2015 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.
 
 import("//build/config/ios/rules.gni")
 import("//build/config/mac/base_rules.gni")
 import("//build/mac/tweak_info_plist.gni")
 import("//ios/build/chrome_build.gni")
 import("//ios/public/provider/chrome/browser/build_config.gni")
 
@@ skipping 259 matching lines @@
     ":main",
     "//ios/chrome/app:tests_fake_hook",
   ]
 
   bundle_deps = [ "//ios/chrome/app/resources" ]
 
   if (ios_enable_today_extension && current_toolchain == default_toolchain) {
     deps += [ ":today_extension_bundle" ]
   }
 
+  if (!ios_enable_today_extension && ios_enable_proto_today_extension &&

[sdefresne, 2017/01/17 10:39:07]

I +1-ing olivierrobin earlier comment (use assert to check that only one of the
two extension is enabled), then change this to:

  if (ios_enable_proto_today_extension && current_toolchain ==
default_toolchain) {
    ... 
  }

BTW, I would even recommend refactoring this to the following:

  if (current_toolchain == default_toolchain) {
    if (ios_enable_today_extension) {
      deps += [ ":today_extension_bundle" ]
    }
    if (ios_enable_proto_today_extension) {
      deps += [ ":proto_today_extension_bundle" ]
    }
    if (ios_enable_share_extension) {
      deps += [ ":share_extension_bundle" ]
    }
  }

[lody, 2017/01/17 17:31:45]

Done.

+      current_toolchain == default_toolchain) {
+    deps += [ ":proto_today_extension_bundle" ]
+  }
+
   if (ios_enable_share_extension && current_toolchain == default_toolchain) {
     deps += [ ":share_extension_bundle" ]
   }
 
   extra_substitutions = [
     "CHROMIUM_BUNDLE_ID=$chromium_bundle_id",
     "CHROMIUM_HANDOFF_ID=$chromium_handoff_id",
     "CHROMIUM_SHORT_NAME=$chromium_short_name",
     "CHROMIUM_URL_SCHEME_1=$url_unsecure_scheme",
     "CHROMIUM_URL_SCHEME_2=$url_secure_scheme",
@@ skipping 15 matching lines @@
     ]
     sources = [
       "$root_out_dir/today_extension.appex",
     ]
     outputs = [
       "{{bundle_plugins_dir}}/{{source_file_part}}",
     ]
   }
 }
 
+if (!ios_enable_today_extension && ios_enable_proto_today_extension &&

[sdefresne, 2017/01/17 10:39:07]

ditto, I would recommend refactoring this to

if (current_toolchain == default_toolchain) {
  if (ios_enable_today_extension) {
    bundle_data("today_extension_bundle") {
      ...
    }
  }
  if (ios_enable_proto_today_extension) {
    bundle_data("proto_today_extension_bundle") {
      ..
    }
  }
  ..
}

[lody, 2017/01/17 17:31:45]

Done.

+    current_toolchain == default_toolchain) {
+  bundle_data("proto_today_extension_bundle") {
+    public_deps = [
+      "//ios/chrome/proto_today_extension",
+    ]
+    sources = [
+      "$root_out_dir/proto_today_extension.appex",
+    ]
+    outputs = [
+      "{{bundle_plugins_dir}}/{{source_file_part}}",
+    ]
+  }
+}
+
 if (ios_enable_share_extension && current_toolchain == default_toolchain) {
   bundle_data("share_extension_bundle") {
     public_deps = [
       "//ios/chrome/share_extension",
     ]
     sources = [
       "$root_out_dir/share_extension.appex",
     ]
     outputs = [
       "{{bundle_plugins_dir}}/{{source_file_part}}",
@@ skipping 73 matching lines @@
     "app_delegate.mm",
   ]
 
   configs += [ "//build/config/compiler:enable_arc" ]
 
   deps = [
     ":application_state_clean_skeleton",
     "//ios/chrome/app/steps",
   ]
 }