[tracing] Adding task information to heap profiler

base/trace_event/heap_profiler_allocation_context_tracker.cc

Index: base/trace_event/heap_profiler_allocation_context_tracker.cc
diff --git a/base/trace_event/heap_profiler_allocation_context_tracker.cc b/base/trace_event/heap_profiler_allocation_context_tracker.cc
index b0e208eb6118b7eaa2e5b2d437c679e09358b54f..842441d6185b2e469d33707d8cf23c93ee1e1bc4 100644
--- a/base/trace_event/heap_profiler_allocation_context_tracker.cc
+++ b/base/trace_event/heap_profiler_allocation_context_tracker.cc
@@ -8,6 +8,7 @@
 #include <iterator>
 
 #include "base/atomicops.h"
+#include "base/compiler_specific.h"
 #include "base/threading/thread_local_storage.h"
 #include "base/trace_event/heap_profiler_allocation_context.h"
 
@@ -19,6 +20,7 @@ subtle::Atomic32 AllocationContextTracker::capture_enabled_ = 0;
 namespace {
 
 const size_t kMaxStackDepth = 128u;
+const size_t kMaxTaskDepth = 16u;
 AllocationContextTracker* const kInitializingSentinel =
     reinterpret_cast<AllocationContextTracker*>(-1);
 
@@ -32,6 +34,24 @@ void DestructAllocationContextTracker(void* alloc_ctx_tracker) {
 
 }  // namespace
 
+AllocationContextTracker::ScopedTaskExecutionEvent::ScopedTaskExecutionEvent(
+    const char* category_group,
+    const char* posted_reason)
+    : category_(category_group) {
+  if (UNLIKELY(capture_enabled())) {
+    AllocationContextTracker* tracker = GetInstanceForCurrentThread();
+    tracker->PushCurrentCategoryName(category_);
+  }
+}
+
+AllocationContextTracker::ScopedTaskExecutionEvent::
+    ~ScopedTaskExecutionEvent() {
+  if (UNLIKELY(capture_enabled())) {
+    AllocationContextTracker* tracker = GetInstanceForCurrentThread();
+    tracker->PopCurrentCategoryName(category_);
+  }
+}
+
 // static
 AllocationContextTracker*
 AllocationContextTracker::GetInstanceForCurrentThread() {
@@ -51,6 +71,7 @@ AllocationContextTracker::GetInstanceForCurrentThread() {
 
 AllocationContextTracker::AllocationContextTracker() {
   pseudo_stack_.reserve(kMaxStackDepth);
+  categories_.reserve(kMaxTaskDepth);
 }
 AllocationContextTracker::~AllocationContextTracker() {}
 
@@ -122,10 +143,27 @@ AllocationContext AllocationContextTracker::GetContextSnapshot() {
     std::fill(dst, dst_end, nullptr);
   }
 
-  ctx.type_name = nullptr;
+  // Set the default type name to file name where the task was posted from.
+  // TODO(ssid): Fix crbug.com/594803 to add file name as 3rd dimension
+  // (component name) in the heap profiler and not piggy back on the type name.
+  ctx.type_name = categories_.empty() ? nullptr : categories_.back();
 
   return ctx;
 }
 
+void AllocationContextTracker::PushCurrentCategoryName(const char* category) {
+  DCHECK(category != nullptr);

[Primiano Tucci (use gerrit), 2016/03/25 01:56:31]

I think as a general stylistic pattern we don't bother with != nullptr, just
DCHECK(category) should be file.
Also rename the arg :) 

[ssid, 2016/03/28 18:14:49]

Done.

+  if (categories_.size() < kMaxTaskDepth)
+    categories_.push_back(category);
+  else
+    NOTREACHED();
+}
+
+void AllocationContextTracker::PopCurrentCategoryName(const char* category) {
+  DCHECK_EQ(category, categories_.back())
+      << "Encountered an unmatched category end";
+  categories_.pop_back();
+}
+
 }  // namespace trace_event
 }  // namespace base