tools/gn: depend on malloc_dump_provider.cc to keep bootstrap working

This patch adds the missing base/trace_event/malloc_dump_provider.cc to
the sources list to keep the boostrap process working and to fix the
undefined reference error as below:

Undefined symbols for architecture x86_64:
  "base::trace_event::MallocDumpProvider::GetInstance()", referenced from:
      base::trace_event::MemoryDumpManager::Initialize(base::trace_event::MemoryDumpManagerDelegate*, bool) in base.a(memory_dump_manager.o)
  "base::trace_event::MallocDumpProvider::kAllocatedObjects", referenced from:
      base::trace_event::MemoryDumpManager::kSystemAllocatorPoolName in base.a(memory_dump_manager.o)

BUG=568437
TEST=./tools/gn/bootstrap/bootstrap.py
TBR=brettw@chromium.org

Review URL: https://codereview.chromium.org/1517983003

Cr-Original-Commit-Position: refs/heads/master@{#364802}
Cr-Mirrored-From: https://chromium.googlesource.com/chromium/src
Cr-Mirrored-Commit: 8c8cc28366502d308586eec95f8ad919c6dc7ab4
diff --git a/tools/gn/bootstrap/bootstrap.py b/tools/gn/bootstrap/bootstrap.py
index 8581f71..2dba1aa 100755
--- a/tools/gn/bootstrap/bootstrap.py
+++ b/tools/gn/bootstrap/bootstrap.py
@@ -249,6 +249,7 @@
       'base/trace_event/heap_profiler_allocation_context_tracker.cc',
       'base/trace_event/heap_profiler_stack_frame_deduplicator.cc',
       'base/trace_event/heap_profiler_type_name_deduplicator.cc',
+      'base/trace_event/malloc_dump_provider.cc',
       'base/trace_event/memory_allocator_dump.cc',
       'base/trace_event/memory_allocator_dump_guid.cc',
       'base/trace_event/memory_dump_manager.cc',