memory-infra: Add peak-detector skeleton.

base/BUILD.gn

Index: base/BUILD.gn
diff --git a/base/BUILD.gn b/base/BUILD.gn
index 6309613708d8232604665c8a89092bcc2ff3a2a2..1d966a3a80502753f0ac28e5f4820dbbf314cebd 100644
--- a/base/BUILD.gn
+++ b/base/BUILD.gn
@@ -1007,6 +1007,8 @@ component("base") {
     "trace_event/memory_dump_session_state.h",
     "trace_event/memory_infra_background_whitelist.cc",
     "trace_event/memory_infra_background_whitelist.h",
+    "trace_event/memory_peak_detector.cc",
+    "trace_event/memory_peak_detector.h",
     "trace_event/memory_usage_estimator.cc",
     "trace_event/memory_usage_estimator.h",
     "trace_event/process_memory_dump.cc",
@@ -2171,6 +2173,7 @@ test("base_unittests") {
     "trace_event/memory_allocator_dump_unittest.cc",
     "trace_event/memory_dump_manager_unittest.cc",
     "trace_event/memory_dump_scheduler_unittest.cc",
+    "trace_event/memory_peak_detector_unittest.cc",
     "trace_event/memory_usage_estimator_unittest.cc",
     "trace_event/process_memory_dump_unittest.cc",
     "trace_event/trace_category_unittest.cc",