Disable timing from chrome://profiler on Android.

base/profiler/tracked_time.cc

Index: base/profiler/tracked_time.cc
diff --git a/base/profiler/tracked_time.cc b/base/profiler/tracked_time.cc
index 7791c3adc6b8580f09ccffd100bc6a2dd241c81f..1c2393f487019a69c0b4995681dcfe871415c9a9 100644
--- a/base/profiler/tracked_time.cc
+++ b/base/profiler/tracked_time.cc
@@ -4,12 +4,36 @@
 
 #include "base/profiler/tracked_time.h"
 
+#include "base/base_switches.h"
+#include "base/command_line.h"
 #include "build/build_config.h"
 
 #if defined(OS_WIN)
 #include <mmsystem.h>  // Declare timeGetTime()... after including build_config.
 #endif
 
+namespace {
+enum ProfilerTimingState {
+  UNDEFINED_TIMING,
+  ENABLED_TIMING,
+  DISABLED_TIMING,
+} g_timing_enabled = UNDEFINED_TIMING;
+
+inline bool IsProfilerTimingEnabled() {
+  // This initialization is not thread-safe, so the value of |g_timing_enabled|
+  // can be computed multiple time. 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
+
 namespace tracked_objects {
 
 Duration::Duration() : ms_(0) {}
@@ -51,6 +75,8 @@ TrackedTime::TrackedTime(const base::TimeTicks& time)
 
 // static
 TrackedTime TrackedTime::Now() {
+  if (!IsProfilerTimingEnabled())
+    return TrackedTime();

[no sievers, 2013/12/06 20:13:54]

What functionally does this break exactly?
Seems weird to break things inside this function here, rather than properly
disabling whatever the feature is at a higher level.

[jar (doing other things), 2013/12/06 21:57:39]

This stops getting timing... but still gets call counts, etc., providing some
utility (that would be lost if we completely inhibited profiling).

 #if defined(OS_WIN)
   // Use lock-free accessor to 32 bit time.
   // Note that TimeTicks::Now() is built on this, so we have "compatible"