[Sync] Implement MemoryDumpProvider.

components/sync/BUILD.gn

Index: components/sync/BUILD.gn
diff --git a/components/sync/BUILD.gn b/components/sync/BUILD.gn
index 836dd3c91462dd614af68a226ce11d4260a844ff..a72df4d7ea01d53dcccea0996589a6cf56704f07 100644
--- a/components/sync/BUILD.gn
+++ b/components/sync/BUILD.gn
@@ -451,6 +451,8 @@ static_library("sync") {
     "model_impl/shared_model_type_processor.h",
     "protocol/proto_enum_conversions.cc",
     "protocol/proto_enum_conversions.h",
+    "protocol/proto_memory_estimations.cc",
+    "protocol/proto_memory_estimations.h",
     "protocol/proto_value_conversions.cc",
     "protocol/proto_value_conversions.h",
     "protocol/proto_visitors.h",
@@ -902,6 +904,9 @@ source_set("unit_tests") {
     "model_impl/processor_entity_tracker_unittest.cc",
     "model_impl/shared_model_type_processor_unittest.cc",
     "protocol/proto_enum_conversions_unittest.cc",
+    "protocol/proto_memory_estimations_unittest.cc",
+    "protocol/proto_unittest_serialized_data.cc",
+    "protocol/proto_unittest_serialized_data.h",
     "protocol/proto_value_conversions_unittest.cc",
     "syncable/change_record_unittest.cc",
     "syncable/directory_backing_store_unittest.cc",