Support use of third party time function for about:profiler

This uses TCMalloc to provide a time function, allowing
us to see how much memory was allocated on a single thread
during the running of a task.  The alternate time function
is put in place only when a specific environment variable
is detected during TCMalloc startup.

This change currently is activated only in Windows/Linux,
as it is based on changes TCMalloc (not used on Mac).

We also create an infrastructure for using any alternate
timer, to replace the "wall clock time," on a per-thread
basis, in the about:profiler infrastructure.  That interface
may be used on other platforms, including scenarios where
we have a per-thread-CPU-time function to replace the
wall-clock timer.  In all cases, when this alternate timer
is activated, we lose the ability to calculated queueing
time.  Queueing time is based on a time snapshot taken on
a second thread, and hence is not comparable to the
alternate timer (when the alternate timer is engaged).


r=rtenneti
BUG=103321
Review URL: https://chromiumcodereview.appspot.com/9212025

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@122180 0039d316-1c4b-4281-b951-d872f2087c98

1 files changed, 11 insertions, 0 deletions

diff --git a/base/tracked_objects.h b/base/tracked_objects.h
index 96814f6..cd50594 100644
--- a/base/tracked_objects.h
+++ b/base/tracked_objects.h
@@ -17,6 +17,7 @@
 #include "base/gtest_prod_util.h"
 #include "base/lazy_instance.h"
 #include "base/location.h"
+#include "base/profiler/alternate_timer.h"
 #include "base/profiler/tracked_time.h"
 #include "base/time.h"
 #include "base/synchronization/lock.h"
@@ -467,6 +468,12 @@ class BASE_EXPORT ThreadData {
   // the code).
   static TrackedTime Now();
 
+  // Use the function |now| to provide current times, instead of calling the
+  // TrackedTime::Now() function.  Since this alternate function is being used,
+  // the other time arguments (used for calculating queueing delay) will be
+  // ignored.
+  static void SetAlternateTimeSource(NowFunction* now);
+
   // This function can be called at process termination to validate that thread
   // cleanup routines have been called for at least some number of named
   // threads.
@@ -543,6 +550,10 @@ class BASE_EXPORT ThreadData {
   // ThreadData instances.
   static void ShutdownSingleThreadedCleanup(bool leak);
 
+  // When non-null, this specifies an external function that supplies monotone
+  // increasing time functcion.
+  static NowFunction* now_function_;
+
   // We use thread local store to identify which ThreadData to interact with.
   static base::ThreadLocalStorage::StaticSlot tls_index_;