[tracing] Add native allocation tracing mode.

base/trace_event/heap_profiler_allocation_context_tracker.h

Index: base/trace_event/heap_profiler_allocation_context_tracker.h
diff --git a/base/trace_event/heap_profiler_allocation_context_tracker.h b/base/trace_event/heap_profiler_allocation_context_tracker.h
index e5c8c187739b99afaa0f75995b1a534dd14a2e4d..63fb879eb52908c93c71f5c97b7bf4ee4232c5c3 100644
--- a/base/trace_event/heap_profiler_allocation_context_tracker.h
+++ b/base/trace_event/heap_profiler_allocation_context_tracker.h
@@ -9,10 +9,19 @@
 
 #include "base/atomicops.h"
 #include "base/base_export.h"
+#include "base/debug/debugging_flags.h"
+#include "base/debug/stack_trace.h"
 #include "base/logging.h"
 #include "base/macros.h"
 #include "base/trace_event/heap_profiler_allocation_context.h"
 
+#if HAVE_TRACE_STACK_FRAME_POINTERS && !defined(OS_NACL) && \
+    (BUILDFLAG(ENABLE_PROFILING) || defined(DEBUG))

[Primiano Tucci (use gerrit), 2016/04/21 20:08:21]

I think that s/defined(DEBUG)/!defined(NDEBUG)/ is more reliable (40 vs 366
results in codesearch)

+#define ENABLE_NATIVE_ALLOCATION_TRACES 1
+#else
+#define ENABLE_NATIVE_ALLOCATION_TRACES 0
+#endif
+
 namespace base {
 namespace trace_event {
 
@@ -23,24 +32,32 @@ namespace trace_event {
 // details.
 class BASE_EXPORT AllocationContextTracker {
  public:
-  // Globally enables capturing allocation context.
-  // TODO(ruuda): Should this be replaced by |EnableCapturing| in the future?
-  // Or at least have something that guards agains enable -> disable -> enable?
-  static void SetCaptureEnabled(bool enabled);
-
-  // Returns whether capturing allocation context is enabled globally.
-  inline static bool capture_enabled() {
+  enum class CaptureMode: int32_t {
+    DISABLED,       // Don't capture anything
+    PSEUDO_STACK,   // GetContextSnapshot() returns pseudo stack trace
+#if ENABLE_NATIVE_ALLOCATION_TRACES
+    NATIVE_STACK    // GetContextSnapshot() returns native (real) stack trace
+#endif
+  };
+
+  // Globally sets capturing mode.
+  // TODO(primiano): How to guard against *_STACK -> DISABLED -> *_STACK?
+  static void SetCaptureMode(CaptureMode mode);
+
+  // Returns global capturing mode.
+  inline static CaptureMode capture_mode() {

[Primiano Tucci (use gerrit), 2016/04/21 20:08:21]

make sure you sync-up with ssid's change, depending on who lands first :)

     // A little lag after heap profiling is enabled or disabled is fine, it is
     // more important that the check is as cheap as possible when capturing is
     // not enabled, so do not issue a memory barrier in the fast path.
-    if (subtle::NoBarrier_Load(&capture_enabled_) == 0)
-      return false;
+    if (subtle::NoBarrier_Load(&capture_mode_) ==
+            static_cast<int32_t>(CaptureMode::DISABLED))
+      return CaptureMode::DISABLED;
 
     // In the slow path, an acquire load is required to pair with the release
-    // store in |SetCaptureEnabled|. This is to ensure that the TLS slot for
+    // store in |SetCaptureMode|. This is to ensure that the TLS slot for
     // the thread-local allocation context tracker has been initialized if
-    // |capture_enabled| returns true.
-    return subtle::Acquire_Load(&capture_enabled_) != 0;
+    // |capture_mode| returns something other than DISABLED.
+    return static_cast<CaptureMode>(subtle::Acquire_Load(&capture_mode_));
   }
 
   // Returns the thread-local instance, creating one if necessary. Returns
@@ -71,7 +88,7 @@ class BASE_EXPORT AllocationContextTracker {
  private:
   AllocationContextTracker();
 
-  static subtle::Atomic32 capture_enabled_;
+  static subtle::Atomic32 capture_mode_;
 
   // The pseudo stack where frames are |TRACE_EVENT| names.
   std::vector<const char*> pseudo_stack_;