[tracing] Introduce BACKGROUND mode in MemoryInfra

base/trace_event/memory_dump_request_args.cc

Index: base/trace_event/memory_dump_request_args.cc
diff --git a/base/trace_event/memory_dump_request_args.cc b/base/trace_event/memory_dump_request_args.cc
index 48b5ba6d2c0c76314a435e3a18304b91cc63a351..e6c5b87b22684b56f399d6a21bd0f55b4244947a 100644
--- a/base/trace_event/memory_dump_request_args.cc
+++ b/base/trace_event/memory_dump_request_args.cc
@@ -28,6 +28,8 @@ const char* MemoryDumpTypeToString(const MemoryDumpType& dump_type) {
 const char* MemoryDumpLevelOfDetailToString(
     const MemoryDumpLevelOfDetail& level_of_detail) {
   switch (level_of_detail) {
+    case MemoryDumpLevelOfDetail::BACKGROUND:
+      return "background";
     case MemoryDumpLevelOfDetail::LIGHT:
       return "light";
     case MemoryDumpLevelOfDetail::DETAILED:
@@ -39,6 +41,8 @@ const char* MemoryDumpLevelOfDetailToString(
 
 MemoryDumpLevelOfDetail StringToMemoryDumpLevelOfDetail(
     const std::string& str) {
+  if (str == "background")
+    return MemoryDumpLevelOfDetail::BACKGROUND;
   if (str == "light")
     return MemoryDumpLevelOfDetail::LIGHT;
   if (str == "detailed")