Reland of [tracing] Dump child processes' memory metrics in browser

components/tracing/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.
 
 component("tracing") {
   sources = [
     "child_memory_dump_manager_delegate_impl.cc",
     "child_memory_dump_manager_delegate_impl.h",
     "child_trace_message_filter.cc",
     "child_trace_message_filter.h",
     "graphics_memory_dump_provider_android.cc",
     "graphics_memory_dump_provider_android.h",
+    "process_metrics_memory_dump_provider.cc",
+    "process_metrics_memory_dump_provider.h",
     "tracing_export.h",
     "tracing_messages.cc",
     "tracing_messages.h",
   ]
 
   defines = [ "TRACING_IMPLEMENTATION" ]
 
   deps = [
     "//base",
     "//ipc",
   ]
+
+  if (is_nacl) {
+    sources -= [ "process_metrics_memory_dump_provider.cc" ]
+  }
 }
 
 component("startup_tracing") {
   sources = [
     "trace_config_file.cc",
     "trace_config_file.h",
     "trace_to_console.cc",
     "trace_to_console.h",
     "tracing_export.h",
     "tracing_switches.cc",
     "tracing_switches.h",
   ]
 
   defines = [ "TRACING_IMPLEMENTATION" ]
 
   deps = [
     "//base",
   ]
 }
 
 source_set("unit_tests") {
   testonly = true
 
   sources = [
     "graphics_memory_dump_provider_android_unittest.cc",
+    "process_metrics_memory_dump_provider_unittest.cc",
   ]
 
   deps = [
     ":tracing",
     "//base/test:test_support",
     "//testing/gtest",
   ]
 
   if (!is_android) {
     sources += [ "trace_config_file_unittest.cc" ]
     deps += [ ":startup_tracing" ]
   }
 }