[tracing] Introduce BACKGROUND mode in MemoryInfra

third_party/WebKit/public/platform/WebMemoryDumpProvider.h

 // 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.
 
 #ifndef WebMemoryDumpProvider_h
 #define WebMemoryDumpProvider_h
 
 #include "WebCommon.h"
 
 namespace blink {
 
 class WebProcessMemoryDump;
 
 // Used to specify the type of memory dump the WebMemoryDumpProvider should
 // generate on dump requests.
 // TODO(hajimehoshi): Remove this and use base::trace_event::
 // MemoryDumpLevelOfDetail instead.
 enum class WebMemoryDumpLevelOfDetail {
+    Background,
     Light,
     Detailed
 };
 
 // Base interface to be part of the memory tracing infrastructure. Blink classes
 // can implement this interface and register themselves (see
 // Platform::registerMemoryDumpProvider()) to dump stats for their allocators.
 class BLINK_PLATFORM_EXPORT WebMemoryDumpProvider {
 public:
     // Function types for functions that can be called on alloc and free to do
@@ skipping 19 matching lines @@
     virtual bool supportsHeapProfiling() { return false; }
 
     // Called by the memory dump manager to enable heap profiling (with true) or
     // called to disable heap profiling (with false).
     virtual void onHeapProfilingEnabled(bool enabled) {}
 };
 
 } // namespace blink
 
 #endif // WebMemoryDumpProvider_h