[tracing] Add thread name to the pseudo stack of heap profiler

base/trace_event/heap_profiler_allocation_context_tracker.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/heap_profiler_allocation_context_tracker.h"
 
 #include <algorithm>
 #include <iterator>
 
 #include "base/atomicops.h"
@@ skipping 31 matching lines @@
 
   if (!tracker) {
     g_tls_alloc_ctx_tracker.Set(kInitializingSentinel);
     tracker = new AllocationContextTracker();
     g_tls_alloc_ctx_tracker.Set(tracker);
   }
 
   return tracker;
 }
 
-AllocationContextTracker::AllocationContextTracker() {
+AllocationContextTracker::AllocationContextTracker() : thread_name_(nullptr) {
   pseudo_stack_.reserve(kMaxStackDepth);
 }
 AllocationContextTracker::~AllocationContextTracker() {}
 
 // static
+void AllocationContextTracker::SetCurrentThreadName(const char* name) {
+  if (name && capture_enabled()) {
+    GetInstanceForCurrentThread()->thread_name_ = name;
+  }
+}
+
+// static
 void AllocationContextTracker::SetCaptureEnabled(bool enabled) {
   // When enabling capturing, also initialize the TLS slot. This does not create
   // a TLS instance yet.
   if (enabled && !g_tls_alloc_ctx_tracker.initialized())
     g_tls_alloc_ctx_tracker.Initialize(DestructAllocationContextTracker);
 
   // Release ordering ensures that when a thread observes |capture_enabled_| to
   // be true through an acquire load, the TLS slot has been initialized.
   subtle::Release_Store(&capture_enabled_, enabled);
 }
@@ skipping 28 matching lines @@
 AllocationContext AllocationContextTracker::GetContextSnapshot() {
   AllocationContext ctx;
 
   // Fill the backtrace.
   {
     auto src = pseudo_stack_.begin();
     auto dst = std::begin(ctx.backtrace.frames);
     auto src_end = pseudo_stack_.end();
     auto dst_end = std::end(ctx.backtrace.frames);
 
+    // Add the thread name as the first enrty in the backtrace.
+    if (thread_name_) {
+      *dst = thread_name_;

[petrcermak, 2016/03/29 13:07:46]

I think that you should DCHECK that dst < dst_end here.

[ssid, 2016/03/29 18:19:11]

Done.

+      ++dst;
+    }
+
     // Copy as much of the bottom of the pseudo stack into the backtrace as
     // possible.
     for (; src != src_end && dst != dst_end; src++, dst++)
       *dst = *src;
 
     // If there is room for more, fill the remaining slots with empty frames.
     std::fill(dst, dst_end, nullptr);
   }
 
   ctx.type_name = nullptr;
 
   return ctx;
 }
 
 }  // namespace trace_event
 }  // namespace base