[tracing] child-process-side impl for inter-process memory dumps

components/tracing/child_memory_dump_manager_delegate_impl.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 "components/tracing/child_memory_dump_manager_delegate_impl.h"
+
+#include "base/single_thread_task_runner.h"
+#include "components/tracing/child_trace_message_filter.h"
+
+namespace tracing {
+
+// static
+ChildMemoryDumpManagerDelegateImpl*
+ChildMemoryDumpManagerDelegateImpl::GetInstance() {
+  return Singleton<
+      ChildMemoryDumpManagerDelegateImpl,
+      LeakySingletonTraits<ChildMemoryDumpManagerDelegateImpl>>::get();
+}
+
+ChildMemoryDumpManagerDelegateImpl::ChildMemoryDumpManagerDelegateImpl()
+    : ctmf_(nullptr) {
+  base::trace_event::MemoryDumpManager::GetInstance()->SetDelegate(this);
+}
+
+ChildMemoryDumpManagerDelegateImpl::~ChildMemoryDumpManagerDelegateImpl() {
+}
+
+void ChildMemoryDumpManagerDelegateImpl::SetChildTraceMessageFilter(
+    ChildTraceMessageFilter* ctmf) {
+  // Check that we are either registering the CTMF or tearing it down, but not
+  // replacing a valid instance with another one (should never happen).
+  DCHECK(ctmf_ == nullptr || (ctmf == nullptr && ctmf_task_runner_ != nullptr));
+  ctmf_ = ctmf;
+  ctmf_task_runner_ = ctmf ? (ctmf->ipc_message_loop()) : nullptr;
+}
+
+// Invoked in child processes by the MemoryDumpManager.
+void ChildMemoryDumpManagerDelegateImpl::RequestGlobalMemoryDump(
+    const base::trace_event::MemoryDumpRequestArgs& args,
+    const base::trace_event::MemoryDumpCallback& callback) {
+  // Bail out if we receive a dump request from the manager before the
+  // ChildTraceMessageFilter has been initialized.
+  if (!ctmf_task_runner_) {
+    if (!callback.is_null())
+      callback.Run(args.dump_guid, false /* success */);
+    return;
+  }
+
+  // Make sure we access |ctmf_| only on the thread where it leaves to avoid

[dsinclair, 2015/04/03 00:31:13]

nit: did you want leaves, or lives here?

[Primiano Tucci (use gerrit), 2015/04/03 18:00:36]

Oh lives actually. Good catch ;-)

+  // races on shutdown.
+  if (!ctmf_task_runner_->BelongsToCurrentThread()) {
+    ctmf_task_runner_->PostTask(
+        FROM_HERE,
+        base::Bind(&ChildMemoryDumpManagerDelegateImpl::RequestGlobalMemoryDump,
+                   base::Unretained(this), args, callback));
+    return;
+  }
+
+  // The ChildTraceMessageFilter could have been destroyed while hopping on the
+  // right thread. If this is the case, bail out.
+  if (!ctmf_) {
+    if (!callback.is_null())
+      callback.Run(args.dump_guid, false /* success */);
+    return;
+  }
+
+  // Send the request up to the browser process' MessageDumpmanager.
+  ctmf_->SendGlobalMemoryDumpRequest(args, callback);
+}
+
+}  // namespace tracing