[tracing] directly use memory-infra from blink -> base

base/trace_event/memory_dump_provider.h

Index: base/trace_event/memory_dump_provider.h
diff --git a/base/trace_event/memory_dump_provider.h b/base/trace_event/memory_dump_provider.h
index 3b1f13623a7e5367a89c1eb976fdaec12fbf632e..35cbd823d46a42e98b4cb15a7acfa8a1118950a1 100644
--- a/base/trace_event/memory_dump_provider.h
+++ b/base/trace_event/memory_dump_provider.h
@@ -7,9 +7,13 @@
 
 #include "base/base_export.h"
 #include "base/macros.h"
+#include "base/memory/ref_counted.h"
 #include "base/trace_event/memory_dump_request_args.h"
 
 namespace base {
+
+class SingleThreadTaskRunner;
+
 namespace trace_event {
 
 class ProcessMemoryDump;
@@ -23,6 +27,22 @@ struct MemoryDumpArgs {
 // The contract interface that memory dump providers must implement.
 class BASE_EXPORT MemoryDumpProvider {
  public:
+  // Helper methods to register/unregister a memory dump provider.
+  // The MemoryDumpManager does NOT take memory ownership of |dump_provider|,
+  // which is expected to either be a singleton or unregister itself.
+  // If the optional |task_runner| argument is non-null, all the calls to the
+  // |dump_provider| will be issued on the given thread. Otherwise, the |mdp|
+  // should be able to handle calls on arbitrary threads.
+  static void Register(

[Ruud van Asseldonk, 2015/10/08 18:40:54]

Does this introduce two ways of doing the same thing,
|MemoryDumpProvider::Register(mdp)| vs
|MemoryDumpManager::GetInstance()->RegisterDumpProvider(mdp)|? Why is that
required?

+      MemoryDumpProvider* dump_provider,
+      const scoped_refptr<SingleThreadTaskRunner>& task_runner);
+
+  // Similar to Register, but all the calls are guaranteed to happen on the
+  // current thread's task runner.
+  static void RegisterOnCurrentThread(MemoryDumpProvider* dump_provider);
+
+  static void Unregister(MemoryDumpProvider* dump_provider);
+
   // 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