[tracing] Simplify MemoryDumpProvider interface

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_attributes_type_info.cc",
     "memory_allocator_attributes_type_info.h",
     "memory_allocator_dump.cc",
     "memory_allocator_dump.h",
     "memory_dump_manager.cc",
     "memory_dump_manager.h",
-    "memory_dump_provider.cc",
     "memory_dump_provider.h",
     "memory_dump_request_args.h",
     "memory_dump_session_state.cc",
     "memory_dump_session_state.h",
     "process_memory_dump.cc",
     "process_memory_dump.h",
     "process_memory_maps.cc",
     "process_memory_maps.h",
     "process_memory_maps_dump_provider.cc",
     "process_memory_maps_dump_provider.h",
@@ skipping 75 matching lines @@
     "trace_event_win_unittest.cc",
     "winheap_dump_provider_win_unittest.cc",
   ]
 
   deps = [
     "//base/test:test_support",
     "//testing/gmock",
     "//testing/gtest",
   ]
 }