[tracing] Introduce BACKGROUND mode in MemoryInfra

base/trace_event/memory_dump_request_args.cc

 // 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.
 
 #include "base/trace_event/memory_dump_request_args.h"
 
 #include "base/logging.h"
 
 namespace base {
 namespace trace_event {
@@ skipping 10 matching lines @@
     case MemoryDumpType::EXPLICITLY_TRIGGERED:
       return "explicitly_triggered";
   }
   NOTREACHED();
   return "unknown";
 }
 
 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:
       return "detailed";
   }
   NOTREACHED();
   return "unknown";
 }
 
 MemoryDumpLevelOfDetail StringToMemoryDumpLevelOfDetail(
     const std::string& str) {
+  if (str == "background")
+    return MemoryDumpLevelOfDetail::BACKGROUND;
   if (str == "light")
     return MemoryDumpLevelOfDetail::LIGHT;
   if (str == "detailed")
     return MemoryDumpLevelOfDetail::DETAILED;
   NOTREACHED();
   return MemoryDumpLevelOfDetail::LAST;
 }
 
 }  // namespace trace_event
 }  // namespace base