Move enable_pdf to a buildflag header.

chrome/test/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/chrome_build.gni")
 import("//build/config/compiler/compiler.gni")
 import("//build/config/crypto.gni")
 import("//build/config/features.gni")
 import("//build/config/ui.gni")
 import("//chrome/common/features.gni")
@@ skipping 112 matching lines @@
     "//components/toolbar:test_support",
     "//components/update_client:test_support",
     "//components/zoom:test_support",
     "//content/public/app:both",
     "//content/test:test_support",
     "//extensions/features",
     "//gpu/ipc/service",
     "//media:media_features",
     "//net",
     "//net:test_support",
+    "//pdf",
     "//ppapi/features",
     "//printing/features",
     "//skia",
     "//sql",
     "//sql:test_support",
     "//testing/gmock",
     "//testing/gtest",
     "//third_party/zlib",
     "//ui/gfx:test_support",
     "//ui/message_center:test_support",
@@ skipping 77 matching lines @@
     ]
   }
 
   if (use_aura) {
     sources += [
       "base/test_browser_window_aura.cc",
       "base/test_browser_window_aura.h",
     ]
   }
 
-  if (enable_plugins && enable_pdf) {
-    public_deps += [ "//pdf" ]
-  }
-
   if (use_ash) {
     sources += [
       "base/default_ash_event_generator_delegate.cc",
       "base/default_ash_event_generator_delegate.h",
     ]
 
     public_deps += [
       "//ash",
       "//ash/test:ash_with_aura_test_support",
       "//ash/test:test_support_with_content",
@@ skipping 4883 matching lines @@
 }
 
 if (is_win) {
   loadable_module("conflicts_dll") {
     testonly = true
     sources = [
       "conflicts/conflicts_dll.cc",
     ]
   }
 }