[MemoryInfra] Support dump providers running on SequencedTaskRunner

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"
 #include "base/process/process_handle.h"
 #include "base/trace_event/memory_dump_request_args.h"
 
 namespace base {
 namespace trace_event {
 
 class ProcessMemoryDump;
 
 // Args passed to OnMemoryDump(). This is to avoid rewriting all the subclasses
 // in the codebase when extending the MemoryDumpProvider API.
 struct MemoryDumpArgs {
   MemoryDumpLevelOfDetail level_of_detail;
 };
 
 // The contract interface that memory dump providers must implement.
 class BASE_EXPORT MemoryDumpProvider {
  public:
   // Optional arguments for MemoryDumpManager::RegisterDumpProvider().
   struct Options {
-    Options() : target_pid(kNullProcessId) {}
-    explicit Options(ProcessId target_pid) : target_pid(target_pid) {}
+    Options()
+        : target_pid(kNullProcessId),
+          dumps_on_single_thread_task_runner(false) {}
 
     // If the dump provider generates dumps on behalf of another process,
-    // |target_process| contains the pid of that process.
+    // |target_pid| contains the pid of that process.
     // The default value is kNullProcessId, which means that the dump provider
     // generates dumps for the current process.
     ProcessId target_pid;
+
+    // |dumps_on_single_thread_task_runner| is true if the dump provider runs on
+    // a SingleThreadTaskRunner, which is usually the case. It is faster to run
+    // all providers that run on the same thread together without thread hops.
+    bool dumps_on_single_thread_task_runner;
   };
 
   virtual ~MemoryDumpProvider() {}
 
   // 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;
 
   // Called by the MemoryDumpManager when an allocator should start or stop
   // collecting extensive allocation data, if supported.
   virtual void OnHeapProfilingEnabled(bool enabled) {}
 
  protected:
   MemoryDumpProvider() {}
 
   DISALLOW_COPY_AND_ASSIGN(MemoryDumpProvider);
 };
 
 }  // namespace trace_event
 }  // namespace base
 
 #endif  // BASE_TRACE_EVENT_MEMORY_DUMP_PROVIDER_H_