Add rtc_use_memcheck flag, update MB and GN to handle it, and add gni files listing the runtime deps

webrtc/test/BUILD.gn

 # Copyright (c) 2014 The WebRTC project authors. All Rights Reserved.
 #
 # Use of this source code is governed by a BSD-style license
 # that can be found in the LICENSE file in the root of the source
 # tree. An additional intellectual property rights grant can be found
 # in the file PATENTS.  All contributing project authors may
 # be found in the AUTHORS file in the root of the source tree.
 
 import("../build/webrtc.gni")
 import("//build/config/ui.gni")
 if (is_android) {
   import("//build/config/android/rules.gni")
 }
+if (rtc_use_memcheck) {
+  import("//tools/valgrind-webrtc/valgrind-webrtc.gni")
+}
 
 group("test") {
   testonly = true
 
   deps = [
     ":field_trial",
     ":rtp_test_utils",
     ":test_common",
     ":test_renderer",
     ":test_support",
@@ skipping 120 matching lines @@
     configs += [ "//build/config/compiler:enable_arc" ]
   }
 
   if (use_x11) {
     deps += [ "//tools/xdisplaycheck" ]
   }
 
   if (is_android) {
     deps += [ "//base:base" ]
   }
+
+  if (rtc_use_memcheck) {
+    data = valgrind_webrtc_dependencies
+  }
 }
 
 # Depend on this target when you want to have test_support but also the
 # main method needed for gtest to execute!
 rtc_source_set("test_support_main") {
   testonly = true
 
   sources = [
     "run_all_unittests.cc",
     "test_suite.cc",
@@ skipping 245 matching lines @@
     suppressed_configs += [ "//build/config/clang:find_bad_constructs" ]
   }
 
   deps = [
     ":test_support",
     ":video_test_common",
     "../modules/media_file",
     "//testing/gtest",
   ]
 }