Disable timing from chrome://profiler on Android.

base/tracked_objects.cc

Index: base/tracked_objects.cc
diff --git a/base/tracked_objects.cc b/base/tracked_objects.cc
index 0847d5f9163622cd65449707775fe7594de9a2b1..4916c2de0292e2c93858cd12bc0623c711e2baf4 100644
--- a/base/tracked_objects.cc
+++ b/base/tracked_objects.cc
@@ -7,6 +7,8 @@
 #include <limits.h>
 #include <stdlib.h>
 
+#include "base/base_switches.h"
+#include "base/command_line.h"
 #include "base/compiler_specific.h"
 #include "base/debug/leak_annotations.h"
 #include "base/logging.h"
@@ -51,6 +53,25 @@ const ThreadData::Status kInitialStartupState =
 // problem with its presence).
 static const bool kAllowAlternateTimeSourceHandling = true;
 
+inline bool IsProfilerTimingEnabled() {
+  enum {

[no sievers, 2013/12/09 20:10:23]

missing static

[qsr, 2013/12/11 09:11:21]

Done.

+    UNDEFINED_TIMING,
+    ENABLED_TIMING,
+    DISABLED_TIMING,
+  } g_timing_enabled = UNDEFINED_TIMING;

[jar (doing other things), 2013/12/09 20:31:34]

It probably *should* be a global static per the g_* prefix, or something similar
in an anonymous file-scope namespace.  That way it won't bother with
initialization checking, rather than "just" a function static which would
(perchance with barriers etc.).

You'll probably get a thread sanitizer complaint... but that seems acceptable. 
If necessary, you could use atomics.

[Mark Mentovai, 2013/12/09 20:42:39]

jar wrote:
Yes, drop the g_ prefix and put on the “static” keyword as noted by sievers.
Huh?

How would access to a file-scoped static be handled any differently than access
to a function-scoped one? An integer constant-initialized static can be in BSS
or the data segment whether it’s file-scoped or function-scoped.

[jar (doing other things), 2013/12/09 20:47:55]

<doh>  My mistaken... function statics don't need the fancy handling when they
are known at link time... and are the same as file scope statics.  I don't know
what I was thinking.

[qsr, 2013/12/11 09:11:21]

Done.

+  // This initialization is not thread-safe, so the value of |g_timing_enabled|
+  // can be computed multiple times. This is not an issue, as the computed value
+  // will always be the same, and is side-effect free.
+  if (g_timing_enabled == UNDEFINED_TIMING) {
+    g_timing_enabled = (CommandLine::ForCurrentProcess()->GetSwitchValueASCII(
+                            switches::kProfilerTiming) ==
+                        switches::kProfilerTimingDisabledValue)
+                           ? DISABLED_TIMING
+                           : ENABLED_TIMING;
+  }
+  return g_timing_enabled == ENABLED_TIMING;
+}
+
 }  // namespace
 
 //------------------------------------------------------------------------------
@@ -754,7 +775,7 @@ void ThreadData::SetAlternateTimeSource(NowFunction* now_function) {
 TrackedTime ThreadData::Now() {
   if (kAllowAlternateTimeSourceHandling && now_function_)
     return TrackedTime::FromMilliseconds((*now_function_)());
-  if (kTrackAllTaskObjects && TrackingStatus())
+  if (kTrackAllTaskObjects && IsProfilerTimingEnabled() && TrackingStatus())
     return TrackedTime::Now();
   return TrackedTime();  // Super fast when disabled, or not compiled.
 }