Generate globally (cross-process) unique IDs for memory tracing dumps

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 "base/atomic_sequence_num.h"
 #include "base/compiler_specific.h"
@@ skipping 88 matching lines @@
 }
 
 void MemoryDumpManager::RequestDumpPoint(DumpPointType dump_point_type) {
   // TODO(primiano): this will have more logic to coordinate dump points across
   // multiple processes via IPC. See crbug.com/462930.
 
   // Bail out immediately if tracing is not enabled at all.
   if (!UNLIKELY(subtle::NoBarrier_Load(&memory_tracing_enabled_)))
     return;
 
-  // TODO(primiano): Make guid actually unique (cross-process) by hashing it
-  // with the PID. See crbug.com/462931 for details.
-  const uint64 guid = g_next_guid.GetNext();
+  const uint64 guid = base::trace_event::TraceLog::GetInstance()->HashEventId(

[Primiano Tucci (use gerrit), 2015/04/13 22:13:58]

nit: no need for base::trace_event as you are already in the namespace

+      g_next_guid.GetNext());
   CreateLocalDumpPoint(dump_point_type, guid);
 }
 
 void MemoryDumpManager::BroadcastDumpRequest() {
   NOTREACHED();  // TODO(primiano): implement IPC synchronization.
 }
 
 // Creates a dump point for the current process and appends it to the trace.
 void MemoryDumpManager::CreateLocalDumpPoint(DumpPointType dump_point_type,
                                              uint64 guid) {
@@ skipping 53 matching lines @@
 }
 
 void MemoryDumpManager::OnTraceLogDisabled() {
   AutoLock lock(lock_);
   dump_providers_enabled_.clear();
   subtle::NoBarrier_Store(&memory_tracing_enabled_, 0);
 }
 
 }  // namespace trace_event
 }  // namespace base