[tracing] Add support to pre-load and merge ProcessMemoryDump(s).

base/trace_event/BUILD.gn

 # Copyright 2015 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.
 
 source_set("trace_event") {
   sources = [
     "java_heap_dump_provider_android.cc",
     "java_heap_dump_provider_android.h",
     "memory_allocator_dump.cc",
     "memory_allocator_dump.h",
@@ skipping 70 matching lines @@
 
   visibility = [ "//base/*" ]
 }
 
 source_set("trace_event_unittests") {
   testonly = true
   sources = [
     "java_heap_dump_provider_android_unittest.cc",
     "memory_allocator_dump_unittest.cc",
     "memory_dump_manager_unittest.cc",
+    "process_memory_dump_unittest.cc",
     "process_memory_maps_dump_provider_unittest.cc",
     "process_memory_totals_dump_provider_unittest.cc",
     "trace_event_argument_unittest.cc",
     "trace_event_memory_unittest.cc",
     "trace_event_synthetic_delay_unittest.cc",
     "trace_event_system_stats_monitor_unittest.cc",
     "trace_event_unittest.cc",
     "trace_event_win_unittest.cc",
     "winheap_dump_provider_win_unittest.cc",
   ]
 
   deps = [
     "//base/test:test_support",
     "//testing/gmock",
     "//testing/gtest",
   ]
 }