Only build various flash/pnacl/ppapi code when they are enabled.

chrome/browser/BUILD.gn

 # Copyright 2014 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/crypto.gni")
 import("//build/config/features.gni")
 import("//build/config/ui.gni")
 import("//components/nacl/nacl_defines.gni")
 import("//tools/grit/grit_rule.gni")
 
@@ skipping 150 matching lines @@
       "//components/web_modal",
       "//content/app/resources",
       "//media",
       "//media/cast:net",
       "//mojo/environment:chromium",
       "//mojo/public/cpp/bindings",
       "//mojo/public/js/bindings",
       "//mojo/system",
       "//net:net_with_v8",
       "//third_party/WebKit/public:resources",
-      "//third_party/adobe/flash:flapper_version_h",
       "//third_party/expat",
       "//third_party/leveldatabase",
       "//third_party/libaddressinput",
       "//third_party/libyuv",
       "//third_party/npapi",
       "//third_party/re2",
       "//third_party/smhasher:cityhash",
       "//ui/gl",
       "//ui/surface",
       "//ui/web_dialogs",
@@ skipping 117 matching lines @@
     # Configuration policy disabled.
     sources += rebase_path(gypi_values.chrome_browser_policy_disabled_sources,
                            ".", "//chrome")
   }
 
   if (enable_plugins) {
     sources += rebase_path(gypi_values.chrome_browser_plugins_sources,
                            ".", "//chrome")
     deps += [
       "//ppapi:ppapi_ipc",
+      "//third_party/adobe/flash:flapper_version_h",
     ]
   }
   if (safe_browsing_mode != 0) {
     sources += rebase_path(
         gypi_values.chrome_browser_basic_safe_browsing_sources,
         ".", "//chrome")
     deps += [
       "//chrome/browser/safe_browsing:chunk_proto",
       "//chrome/browser/safe_browsing:report_proto",
     ]
@@ skipping 342 matching lines @@
 # TODO(GYP) write internal action
 if (false) {  #if (is_chrome_branded) {
   action("chrome_internal_resources_gen") {
     # TODO(GYP)
   }
 } else {
   group("chrome_internal_resources_gen") {
     # Empty placeholder.
   }
 }