Remove hotword installation code at compile time if hotwording disabled.

build/config/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.
 
 import("//build/config/allocator.gni")
 import("//build/config/chrome_build.gni")
 import("//build/config/crypto.gni")
 import("//build/config/features.gni")
 import("//build/config/ui.gni")
 import("//build/module_args/v8.gni")
@@ skipping 19 matching lines @@
   dcheck_always_on = false
 
   # Set to true to compile with the OpenGL ES 2.0 conformance tests.
   internal_gles2_conform_tests = false
 }
 
 # TODO(brettw) Most of these should be removed. Instead of global feature
 # flags, we should have more modular flags that apply only to a target and its
 # dependents. For example, depending on the "x11" meta-target should define
 # USE_X11 for all dependents so that everything that could use X11 gets the
 # define, but anything that doesn't depend on X11 doesn't see it.

[Nico, 2015/06/24 19:34:04]

Have you seen this comment? Is it possible to do something like it suggests for
your flag?

[Matt Giuca, 2015/06/25 03:13:18]

No I didn't see that before, sorry.

This sounds like a dangerous rule. I've already broken the build twice now
(https://codereview.chromium.org/1199343003/ and http://crbug.com/503963) due to
adding #if defined(ENABLE_HOTWORDING) in files where that flag was not
available. We can't test for this, since it's based on a compile-time flag (the
tests have to pass whether the flag is on or off, and we can't test both code
paths on the main builders).

I'd prefer to keep this here since it will already be used in three places
(chrome/browser/extensions, chrome/browser/search and chrome/browser/search
unit_tests). If you feel strongly about it, I'll try to make the flag available
in just those three places but I think this is asking for more bugs.

Note: Is this just a GN issue or does it also have to be fixed for GYP?

 #
 # For now we define these globally to match the current GYP build.
 config("feature_flags") {
   # TODO(brettw) this probably needs to be parameterized.
   defines = [ "V8_DEPRECATION_WARNINGS" ]  # Don't use deprecated V8 APIs anywhere.
 
   if (cld_version > 0) {
     defines += [ "CLD_VERSION=$cld_version" ]
   }
   if (enable_mdns) {
@@ skipping 214 matching lines @@
     defines += [ "OFFICIAL_BUILD" ]
   }
   if (is_chrome_branded) {
     defines += [ "GOOGLE_CHROME_BUILD" ]
   } else {
     defines += [ "CHROMIUM_BUILD" ]
   }
   if (enable_media_router) {
     defines += [ "ENABLE_MEDIA_ROUTER=1" ]
   }
+  if (enable_hotwording) {
+    defines += [ "ENABLE_HOTWORDING" ]
+  }
 }
 
 # Debug/release ----------------------------------------------------------------
 
 config("debug") {
   defines = [
     "_DEBUG",
     "DYNAMIC_ANNOTATIONS_ENABLED=1",
     "WTF_USE_DYNAMIC_ANNOTATIONS=1",
   ]
@@ skipping 104 matching lines @@
       "CoreFoundation.framework",
       "CoreGraphics.framework",
       "CoreText.framework",
       "Foundation.framework",
       "UIKit.framework",
     ]
   } else if (is_linux) {
     libs = [ "dl" ]
   }
 }