Land prep work to enable NaCl in the Linux x64 GN builds.

base/BUILD.gn

Index: base/BUILD.gn
diff --git a/base/BUILD.gn b/base/BUILD.gn
index 43f92f501937244a55ceb6f24208d285ca0926bd..d1fc296297ac1cbcf225e4809301829779f71349 100644
--- a/base/BUILD.gn
+++ b/base/BUILD.gn
@@ -756,7 +756,29 @@ component("base") {
   ]
 
   if (is_nacl) {
-    sources += [ "files/file_path_watcher_stub.cc" ]
+    # We reset sources_assignment_filter in order to explicitly include
+    # the linux file (which would otherwise be filtered out).
+    set_sources_assignment_filter([])
+    sources += [
+      "files/file_path_watcher_stub.cc",
+      "sync_socket_nacl.cc",
+      "threading/platform_thread_linux.cc",
+    ]
+    set_sources_assignment_filter(sources_assignment_filter)
+
+    sources -= [
+      "allocator/type_profiler_control.cc",
+      "allocator/type_profiler_control.h",
+      "async_socket_io_handler_posix.cc",
+      "base_paths.cc",
+      "cpu.cc",
+      "files/file_proxy.cc",
+      "files/file_util.cc",
+      "files/file_util_proxy.cc",
+      "path_service.cc",
+      "scoped_native_library.cc",
+      "files/scoped_temp_dir.cc",
+    ]
   }
 
   sources -= [
@@ -775,11 +797,14 @@ component("base") {
   deps = [
     ":base_static",
     "//base/allocator:allocator_extension_thunks",
-    "//base/third_party/dynamic_annotations",
     "//base/third_party/nspr",
     "//third_party/modp_b64",
   ]
 
+  if (!is_nacl) {
+    deps += [ "//base/third_party/dynamic_annotations" ]
+  }
+
   # Allow more direct string conversions on platforms with native utf8
   # strings
   if (is_mac || is_ios || is_chromeos) {
@@ -836,14 +861,15 @@ component("base") {
       "debug/stack_trace_posix.cc",
       "files/file_enumerator_posix.cc",
       "files/file_util_posix.cc",
+      "memory/shared_memory_posix.cc",
       "message_loop/message_pump_libevent.cc",
+      "metrics/field_trial.cc",
+      "native_library_posix.cc",
       "process/kill_posix.cc",
       "process/launch_posix.cc",
       "process/process_metrics_posix.cc",
       "process/process_posix.cc",
-      "metrics/field_trial.cc",
-      "native_library_posix.cc",
-      "memory/shared_memory_posix.cc",
+      "rand_util_posix.cc",
       "sync_socket_posix.cc",
       "sys_info_posix.cc",
     ]
@@ -1019,10 +1045,13 @@ component("i18n") {
   configs += [ "//build/config/compiler:wexit_time_destructors" ]
   deps = [
     ":base",
-    "//base/third_party/dynamic_annotations",
     "//third_party/icu",
   ]
 
+  if (!is_nacl) {
+    deps += [ "//base/third_party/dynamic_annotations" ]
+  }
+
   if (is_android && !is_debug) {
     configs -= [ "//build/config/compiler:optimize" ]
     configs += [ "//build/config/compiler:optimize_max" ]