tracing: Make ConvertableToTraceFormat move-only scoped_ptr

base/trace_event/memory_dump_manager.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_manager.h"
 
 #include <algorithm>
 #include <utility>
 
 #include "base/atomic_sequence_num.h"
@@ skipping 60 matching lines @@
   TRACE_EVENT_NESTABLE_ASYNC_END1(
       MemoryDumpManager::kTraceCategory, "GlobalMemoryDump",
       TRACE_ID_MANGLE(dump_guid), "success", success);
 
   if (!wrapped_callback.is_null()) {
     wrapped_callback.Run(dump_guid, success);
     wrapped_callback.Reset();
   }
 }
 
+// Proxy class which wraps a ConvertableToTraceFormat owned by the
+// |session_state| into a proxy object that can be added to the trace event log.
+// This is to solve the problem that the MemoryDumpSessionState is refcounted
+// but the tracing subsystem wants a scoped_ptr<ConvertableToTraceFormat>.
+template <typename T>
+struct SessionStateConvertableProxy : public ConvertableToTraceFormat {
+  using GetterFunctPtr = T* (MemoryDumpSessionState::*)() const;
+
+  SessionStateConvertableProxy(
+      scoped_refptr<MemoryDumpSessionState> session_state,
+      GetterFunctPtr getter_function)
+      : session_state(session_state), getter_function(getter_function) {}
+
+  void AppendAsTraceFormat(std::string* out) const override {
+    return (session_state.get()->*getter_function)()->AppendAsTraceFormat(out);
+  }
+
+  void EstimateTraceMemoryOverhead(
+      TraceEventMemoryOverhead* overhead) override {
+    return (session_state.get()->*getter_function)()
+        ->EstimateTraceMemoryOverhead(overhead);
+  }
+
+  scoped_refptr<MemoryDumpSessionState> session_state;
+  GetterFunctPtr const getter_function;
+};
+
 }  // namespace
 
 // static
 const char* const MemoryDumpManager::kTraceCategory =
     TRACE_DISABLED_BY_DEFAULT("memory-infra");
 
 // static
 const int MemoryDumpManager::kMaxConsecutiveFailuresCount = 3;
 
 // static
@@ skipping 429 matching lines @@
     return;
   }
 
   TRACE_EVENT_WITH_FLOW0(kTraceCategory,
                          "MemoryDumpManager::FinalizeDumpAndAddToTrace",
                          TRACE_ID_MANGLE(dump_guid), TRACE_EVENT_FLAG_FLOW_IN);
 
   for (const auto& kv : pmd_async_state->process_dumps) {
     ProcessId pid = kv.first;  // kNullProcessId for the current process.
     ProcessMemoryDump* process_memory_dump = kv.second.get();
-    TracedValue* traced_value = new TracedValue();
-    scoped_refptr<ConvertableToTraceFormat> event_value(traced_value);
+    TracedValue* traced_value = new TracedValue;
+    scoped_ptr<ConvertableToTraceFormat> event_value(traced_value);

[oystein (OOO til 10th of July), 2016/02/26 19:46:55]

This looks a bit funky. Why do we still keep the raw pointer around here?

[Primiano Tucci (use gerrit), 2016/02/26 22:52:49]

Ah it was a funky way to get around the fact that TRACE_EVENT_API wants a
_ptr<CTTF>* but here we have and need a _ptr<TracedValue>.
But now with std::move semantics is easier to convert. Done

     process_memory_dump->AsValueInto(traced_value);
     traced_value->SetString("level_of_detail",
                             MemoryDumpLevelOfDetailToString(
                                 pmd_async_state->req_args.level_of_detail));
     const char* const event_name =
         MemoryDumpTypeToString(pmd_async_state->req_args.dump_type);
 
     TRACE_EVENT_API_ADD_TRACE_EVENT_WITH_PROCESS_ID(
         TRACE_EVENT_PHASE_MEMORY_DUMP,
         TraceLog::GetCategoryGroupEnabled(kTraceCategory), event_name,
@@ skipping 31 matching lines @@
   // Spin-up the thread used to invoke unbound dump providers.
   scoped_ptr<Thread> dump_thread(new Thread("MemoryInfra"));
   if (!dump_thread->Start()) {
     LOG(ERROR) << "Failed to start the memory-infra thread for tracing";
     return;
   }
 
   AutoLock lock(lock_);
 
   DCHECK(delegate_);  // At this point we must have a delegate.
-
-  scoped_refptr<StackFrameDeduplicator> stack_frame_deduplicator = nullptr;
-  scoped_refptr<TypeNameDeduplicator> type_name_deduplicator = nullptr;
+  session_state_ = new MemoryDumpSessionState;
 
   if (heap_profiling_enabled_) {
     // If heap profiling is enabled, the stack frame deduplicator and type name
     // deduplicator will be in use. Add a metadata events to write the frames
     // and type IDs.
-    stack_frame_deduplicator = new StackFrameDeduplicator;
-    type_name_deduplicator = new TypeNameDeduplicator;
+    session_state_->SetStackFrameDeduplicator(
+        make_scoped_ptr(new StackFrameDeduplicator));
+
+    session_state_->SetTypeNameDeduplicator(
+        make_scoped_ptr(new TypeNameDeduplicator));
+
     TRACE_EVENT_API_ADD_METADATA_EVENT(
         TraceLog::GetCategoryGroupEnabled("__metadata"), "stackFrames",
         "stackFrames",
-        scoped_refptr<ConvertableToTraceFormat>(stack_frame_deduplicator));
+        make_scoped_ptr(
+            new SessionStateConvertableProxy<StackFrameDeduplicator>(
+                session_state_,
+                &MemoryDumpSessionState::stack_frame_deduplicator)));
+
     TRACE_EVENT_API_ADD_METADATA_EVENT(
         TraceLog::GetCategoryGroupEnabled("__metadata"), "typeNames",
         "typeNames",
-        scoped_refptr<ConvertableToTraceFormat>(type_name_deduplicator));
+        make_scoped_ptr(new SessionStateConvertableProxy<TypeNameDeduplicator>(
+            session_state_, &MemoryDumpSessionState::type_name_deduplicator)));
   }
 
   DCHECK(!dump_thread_);
   dump_thread_ = std::move(dump_thread);
-  session_state_ = new MemoryDumpSessionState(stack_frame_deduplicator,
-                                              type_name_deduplicator);
-
   subtle::NoBarrier_Store(&memory_tracing_enabled_, 1);
 
   // TODO(primiano): This is a temporary hack to disable periodic memory dumps
   // when running memory benchmarks until telemetry uses TraceConfig to
   // enable/disable periodic dumps. See crbug.com/529184 .
   if (!is_coordinator_ ||
       CommandLine::ForCurrentProcess()->HasSwitch(
           "enable-memory-benchmarking")) {
     return;
   }
@@ skipping 101 matching lines @@
   auto iter = process_dumps.find(pid);
   if (iter == process_dumps.end()) {
     scoped_ptr<ProcessMemoryDump> new_pmd(new ProcessMemoryDump(session_state));
     iter = process_dumps.insert(std::make_pair(pid, std::move(new_pmd))).first;
   }
   return iter->second.get();
 }
 
 }  // namespace trace_event
 }  // namespace base