Adds ability for chrome to behave as mojo_runner

chrome/BUILD.gn

Index: chrome/BUILD.gn
diff --git a/chrome/BUILD.gn b/chrome/BUILD.gn
index 3ebcf1329c2cc7b8354ebe439b6d4c1376b9f75b..0bf1a46acc762917a7bf8546bde0e540e82ac8c7 100644
--- a/chrome/BUILD.gn
+++ b/chrome/BUILD.gn
@@ -2,6 +2,7 @@
 # Use of this source code is governed by a BSD-style license that can be
 # found in the LICENSE file.
 
+import("//build/buildflag_header.gni")
 import("//build/config/chrome_build.gni")
 import("//build/config/compiler/compiler.gni")
 import("//build/config/features.gni")
@@ -11,6 +12,7 @@ import("//build/config/ui.gni")
 import("//build/config/win/console_app.gni")
 import("//build/config/win/manifest.gni")
 import("//chrome/chrome_repack_locales.gni")
+import("//chrome/mash.gni")
 import("//chrome/version.gni")
 
 declare_args() {
@@ -186,6 +188,7 @@ if (!is_android) {
       }
 
       public_deps = [
+        ":features",
         ":xdg_mime",  # Needs to be public for installer to consume files.
       ]
 
@@ -204,6 +207,10 @@ if (!is_android) {
           "//build/config/linux:xext",
         ]
       }
+
+      if (use_mash) {

[Ben Goodger (Google), 2016/02/22 20:20:00]

you should give this variable a name that implies it's only related to the
packaging of mash components in chrome. as it stands, this variable will be
misused by people in a way that makes it impossible to test without using this
package.

I suggest "package_mash_services"

[sky, 2016/02/23 00:01:33]

I went with the wordy enable_package_mash_services.

+        deps += [ "//chrome/app/mash" ]
+      }
     }
 
     if (is_mac) {
@@ -292,6 +299,7 @@ if (is_mac || is_win) {
 
     deps = [
       ":browser_dependencies",
+      ":features",
       "//build/config/sanitizers:deps",
     ]
     if (is_win) {
@@ -369,6 +377,10 @@ if (is_mac || is_win) {
     if (enable_plugins && enable_pdf && !is_multi_dll_chrome) {
       deps += [ "//pdf" ]
     }
+
+    if (use_mash) {
+      deps += [ "//chrome/app/mash" ]
+    }
   }
 
   if (is_multi_dll_chrome) {
@@ -1097,3 +1109,8 @@ if (is_linux) {
     ]
   }
 }
+
+buildflag_header("features") {
+  header = "chrome_features.h"
+  flags = [ "USE_MASH=$use_mash" ]
+}