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

base/trace_event/trace_event.gypi

 # 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.
 {
   'variables': {
     'trace_event_sources' : [
       'trace_event/java_heap_dump_provider_android.cc',
       'trace_event/java_heap_dump_provider_android.h',
       'trace_event/memory_allocator_dump.cc',
       'trace_event/memory_allocator_dump.h',
@@ skipping 38 matching lines @@
           'trace_event_sources': [
             'trace_event/malloc_dump_provider.cc',
             'trace_event/malloc_dump_provider.h',
           ],
       }],
     ],
     'trace_event_test_sources' : [
       'trace_event/java_heap_dump_provider_android_unittest.cc',
       'trace_event/memory_allocator_dump_unittest.cc',
       'trace_event/memory_dump_manager_unittest.cc',
+      'trace_event/process_memory_dump_unittest.cc',
       'trace_event/process_memory_maps_dump_provider_unittest.cc',
       'trace_event/process_memory_totals_dump_provider_unittest.cc',
       'trace_event/trace_event_argument_unittest.cc',
       'trace_event/trace_event_memory_unittest.cc',
       'trace_event/trace_event_synthetic_delay_unittest.cc',
       'trace_event/trace_event_system_stats_monitor_unittest.cc',
       'trace_event/trace_event_unittest.cc',
       'trace_event/trace_event_win_unittest.cc',
       'trace_event/winheap_dump_provider_win_unittest.cc',
     ],
   },
 }