Record Chrome trace events in tcmalloc heap profiles

third_party/tcmalloc/chromium/src/gperftools/heap-profiler.h

Index: third_party/tcmalloc/chromium/src/gperftools/heap-profiler.h
diff --git a/third_party/tcmalloc/chromium/src/gperftools/heap-profiler.h b/third_party/tcmalloc/chromium/src/gperftools/heap-profiler.h
index 8e3ee962c7126c9f582c022033b95cd71953902e..e432bc77ed42cfc5e67f1ced578a5a79482a0a4a 100644
--- a/third_party/tcmalloc/chromium/src/gperftools/heap-profiler.h
+++ b/third_party/tcmalloc/chromium/src/gperftools/heap-profiler.h
@@ -68,6 +68,8 @@ extern "C" {
 
 /* Start profiling and arrange to write profile data to file names
  * of the form: "prefix.0000", "prefix.0001", ...
+ * |prefix| may be NULL, which prevents writing to disk. This is useful for
+ * applications that exclusively use GetHeapProfile().

[Dai Mikurube (NOT FULLTIME), 2013/06/19 04:34:03]

This comment looks confusing.  The existing profiler assumes that the profiler
is turned off if filename_prefix == NULL.

The comment should explicitly describe which function is allowed, and which
function is disallowed in case of |prefix| == NULL.  E.g. "No writing to disk
while profiling is started if |prefix| == NULL. GetHeapProfile() and ???() are
available, but ???() and ???() cannot be used."  (My English statement might be
improved, though. ;))

[James Cook, 2013/06/29 00:02:42]

Updated the comment. I think the system considers profiling off when |is_on| is
false?  Also, this should be a little clearer now that I'm using
HeapProfilerWithPseudoStackStart().

  */
 PERFTOOLS_DLL_DECL void HeapProfilerStart(const char* prefix);
 
@@ -109,6 +111,14 @@ typedef void (*AddressVisitor)(void* data, const void* ptr);
 PERFTOOLS_DLL_DECL void IterateAllocatedObjects(AddressVisitor callback,
                                                 void* data);
 
+/* Sets a callback function to return a pseudo-stack for application-generated
+ * stacks during heap profiling. The caller must provide a buffer in |stack|
+ * of at least size 32 * sizeof(void*). Returns the number of items copied or
+ * zero.
+ */
+typedef int (*PseudoStackGenerator)(void** stack);
+PERFTOOLS_DLL_DECL void SetPseudoStackGenerator(PseudoStackGenerator callback);
+
 #ifdef __cplusplus
 }  // extern "C"
 #endif