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

chrome/common/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("//tools/grit/grit_rule.gni")
 
 gypi_values = exec_script(
     "//build/gypi_to_gn.py",
     [ rebase_path("../chrome_common.gypi") ],
     "scope",
@@ skipping 75 matching lines @@
       "//chrome/common/extensions/api",
       "//components/visitedlink/common",
       "//components/autofill/content/common",
       "//components/autofill/core/common",
       "//components/password_manager/core/common",
       "//components/signin/core/common",
       "//components/translate/content/common",
       "//extensions/common",
       "//extensions/common/api",
       "//ipc",
-      "//third_party/adobe/flash:flapper_version_h",
       "//third_party/re2",
       "//third_party/widevine/cdm:version_h",
     ]
   }
 
   if (enable_extensions) {
     sources += rebase_path(
         gypi_values.chrome_common_extensions_sources,
         ".", "//chrome")
     deps += [
@@ skipping 96 matching lines @@
     ]
     deps += [
       "//third_party/mach_override",
       "//third_party/google_toolbox_for_mac",
     ]
   }
 
   if (enable_remoting) {
     #deps += [ '../remoting/remoting.gyp:remoting_client_plugin' ]  TODO(GYP)
   }
-  if (!enable_plugins) {
+  if (enable_plugins) {
+    deps += [
+      "//third_party/adobe/flash:flapper_version_h",
+    ]
+  } else {
     sources -= [ "pepper_permission_util.cc" ]
   }
   if (!enable_webrtc) {
     sources -= [ "media/webrtc_logging_messages.h" ]
   }
   if (enable_configuration_policy) {
     deps += [ "//components/policy" ]
   }
 
   if (safe_browsing_mode == 1) {
@@ skipping 56 matching lines @@
     "//components/bookmarks/common",
     "//third_party/widevine/cdm:version_h",
   ]
 
   if (enable_nacl) {
     deps += [
       #'../components/nacl.gyp:nacl_switches',  TODO(GYP)
     ]
   }
 }