[tracing] Reland of Throttle rate of heavy dumps and support to request light/heavy dumps

base/trace_event/memory_dump_provider.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 BASE_TRACE_EVENT_MEMORY_DUMP_PROVIDER_H_
 #define BASE_TRACE_EVENT_MEMORY_DUMP_PROVIDER_H_
 
 #include "base/base_export.h"
 #include "base/macros.h"
 
 namespace base {
 namespace trace_event {
 
 class ProcessMemoryDump;
 
 // Contains information about the type of memory dump the MemoryDumpProvider
 // should generate on dump request. This is to control the size of dumps
 // generated.
 struct MemoryDumpArgs {
-  enum class LevelOfDetail { LOW, HIGH };
+  enum class LevelOfDetail {
+    LOW,
+    HIGH,
+    LAST = HIGH  // For IPC Macros.
+  };
 
   LevelOfDetail level_of_detail;
 };
 
 // The contract interface that memory dump providers must implement.
 class BASE_EXPORT MemoryDumpProvider {
  public:
   // Called by the MemoryDumpManager when generating memory dumps.
   // The |args| specify if the embedder should generate light/heavy dumps on
   // dump requests. The embedder should return true if the |pmd| was
   // successfully populated, false if something went wrong and the dump should
   // be considered invalid.
   // (Note, the MemoryDumpManager has a fail-safe logic which will disable the
   // MemoryDumpProvider for the entire trace session if it fails consistently).
   virtual bool OnMemoryDump(const MemoryDumpArgs& args,
                             ProcessMemoryDump* pmd) = 0;
 
  protected:
   MemoryDumpProvider() {}
   virtual ~MemoryDumpProvider() {}
 
   DISALLOW_COPY_AND_ASSIGN(MemoryDumpProvider);
 };
 
 }  // namespace trace_event
 }  // namespace base
 
 #endif  // BASE_TRACE_EVENT_MEMORY_DUMP_PROVIDER_H_