Disable timing from chrome://profiler on Android.

base/profiler/tracked_time.cc

 // Copyright (c) 2012 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #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) {}
 Duration::Duration(int32 duration) : ms_(duration) {}
 
 Duration& Duration::operator+=(const Duration& other) {
   ms_ += other.ms_;
   return *this;
 }
 
@@ skipping 21 matching lines @@
 //------------------------------------------------------------------------------
 
 TrackedTime::TrackedTime() : ms_(0) {}
 TrackedTime::TrackedTime(int32 ms) : ms_(ms) {}
 TrackedTime::TrackedTime(const base::TimeTicks& time)
     : ms_((time - base::TimeTicks()).InMilliseconds()) {
 }
 
 // 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"
   // times when we down-convert a TimeTicks sample.
   return TrackedTime(base::TimeTicks::UnprotectedNow());
 #else
   // Posix has nice cheap 64 bit times, so we just down-convert it.
   return TrackedTime(base::TimeTicks::Now());
 #endif  // OS_WIN
 }
 
 Duration TrackedTime::operator-(const TrackedTime& other) const {
   return Duration(ms_ - other.ms_);
 }
 
 TrackedTime TrackedTime::operator+(const Duration& other) const {
   return TrackedTime(ms_ + other.ms_);
 }
 
 bool TrackedTime::is_null() const { return ms_ == 0; }
 
 }  // namespace tracked_objects