Revert 217172 "Enable high resolution time for TimeTicks::Now on..."

There is a suspicion that this might break some tests:

MessageLoopTest.PostDelayedTask_InPostOrder_2,
StatsTableTest.StatsCounterTimer
TimeTicks.Deltas

http://build.chromium.org/p/chromium.win/builders/XP%20Tests%20%282%29/builds/30128
http://build.chromium.org/p/chromium.win/builders/Win7%20Tests%20%28dbg%29%281%29/builds/21737

> Enable high resolution time for TimeTicks::Now on Windows Canary
> 
> This should be unnoticeable, except for improved resolution in places such as window.performance.now().
> 
> The feature is enabled if the user is running Canary channel or has manually specified the --enable-high-resolution-time flag. This will only work if the CPU has a non-stop TSC and isn't a broken Athlon processor. UMA data show this is a safe combination.
> 
> The flag is propagated to renderer processes so that they know to enable it too.
> 
> BUG=158234
> 
> Review URL: https://chromiumcodereview.appspot.com/16896018

TBR=simonjam@chromium.org

Review URL: https://codereview.chromium.org/22984005

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@217226 0039d316-1c4b-4281-b951-d872f2087c98

4 files changed, 6 insertions, 57 deletions

diff --git a/base/profiler/tracked_time.cc b/base/profiler/tracked_time.cc
index 7791c3a..27d3358 100644
--- a/base/profiler/tracked_time.cc
+++ b/base/profiler/tracked_time.cc
@@ -55,7 +55,8 @@ TrackedTime TrackedTime::Now() {
   // 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());
+  // TODO(jar): Surface this interface via something in base/time/time.h.
+  return TrackedTime(static_cast<int32>(timeGetTime()));
 #else
   // Posix has nice cheap 64 bit times, so we just down-convert it.
   return TrackedTime(base::TimeTicks::Now());
diff --git a/base/test/test_suite.cc b/base/test/test_suite.cc
index 123663a..27c00c9 100644
--- a/base/test/test_suite.cc
+++ b/base/test/test_suite.cc
@@ -96,7 +96,6 @@ void TestSuite::PreInitialize(int argc, char** argv,
                               bool create_at_exit_manager) {
 #if defined(OS_WIN)
   testing::GTEST_FLAG(catch_exceptions) = false;
-  base::TimeTicks::SetNowIsHighResNowIfSupported();
 #endif
   base::EnableTerminationOnHeapCorruption();
   initialized_command_line_ = CommandLine::Init(argc, argv);
diff --git a/base/time/time.h b/base/time/time.h
index c50bdba..af95700 100644
--- a/base/time/time.h
+++ b/base/time/time.h
@@ -572,17 +572,6 @@ class BASE_EXPORT TimeTicks {
   // Returns true if the high resolution clock is working on this system.
   // This is only for testing.
   static bool IsHighResClockWorking();
-
-  // Enable high resolution time for TimeTicks::Now(). This function will
-  // test for the availability of a working implementation of
-  // QueryPerformanceCounter(). If one is not available, this function does
-  // nothing and the resolution of Now() remains 1ms. Otherwise, all future
-  // calls to TimeTicks::Now() will have the higher resolution provided by QPC.
-  // Returns true if high resolution time was successfully enabled.
-  static bool SetNowIsHighResNowIfSupported();
-
-  // Returns a time value that is NOT rollover protected.
-  static TimeTicks UnprotectedNow();
 #endif
 
   // Returns true if this object has not been initialized.
diff --git a/base/time/time_win.cc b/base/time/time_win.cc
index f35f735..3680ee2a 100644
--- a/base/time/time_win.cc
+++ b/base/time/time_win.cc
@@ -322,12 +322,6 @@ TimeDelta RolloverProtectedNow() {
   return TimeDelta::FromMilliseconds(now + rollover_ms);
 }
 
-bool IsBuggyAthlon(const base::CPU& cpu) {
-  // On Athlon X2 CPUs (e.g. model 15) QueryPerformanceCounter is
-  // unreliable.  Fallback to low-res clock.
-  return cpu.vendor_name() == "AuthenticAMD" && cpu.family() == 15;
-}
-
 // Overview of time counters:
 // (1) CPU cycle counter. (Retrieved via RDTSC)
 // The CPU counter provides the highest resolution time stamp and is the least
@@ -404,8 +398,10 @@ class HighResNowSingleton {
       skew_(0) {
     InitializeClock();
 
+    // On Athlon X2 CPUs (e.g. model 15) QueryPerformanceCounter is
+    // unreliable.  Fallback to low-res clock.
     base::CPU cpu;
-    if (IsBuggyAthlon(cpu))
+    if (cpu.vendor_name() == "AuthenticAMD" && cpu.family() == 15)
       DisableHighResClock();
   }
 
@@ -437,24 +433,6 @@ class HighResNowSingleton {
   friend struct DefaultSingletonTraits<HighResNowSingleton>;
 };
 
-TimeDelta HighResNowWrapper() {
-  return HighResNowSingleton::GetInstance()->Now();
-}
-
-typedef TimeDelta (*NowFunction)(void);
-NowFunction now_function = RolloverProtectedNow;
-
-bool CPUReliablySupportsHighResTime() {
-  base::CPU cpu;
-  if (!cpu.has_non_stop_time_stamp_counter())
-    return false;
-
-  if (IsBuggyAthlon(cpu))
-    return false;
-
-  return true;
-}
-
 }  // namespace
 
 // static
@@ -469,18 +447,8 @@ TimeTicks::TickFunctionType TimeTicks::SetMockTickFunction(
 }
 
 // static
-bool TimeTicks::SetNowIsHighResNowIfSupported() {
-  if (!CPUReliablySupportsHighResTime()) {
-    return false;
-  }
-
-  now_function = HighResNowWrapper;
-  return true;
-}
-
-// static
 TimeTicks TimeTicks::Now() {
-  return TimeTicks() + now_function();
+  return TimeTicks() + RolloverProtectedNow();
 }
 
 // static
@@ -515,14 +483,6 @@ bool TimeTicks::IsHighResClockWorking() {
   return HighResNowSingleton::GetInstance()->IsUsingHighResClock();
 }
 
-TimeTicks TimeTicks::UnprotectedNow() {
-  if (now_function == HighResNowWrapper) {
-    return Now();
-  } else {
-    return TimeTicks() + TimeDelta::FromMilliseconds(timeGetTime());
-  }
-}
-
 // TimeDelta ------------------------------------------------------------------
 
 // static