Simplify base::Timer implementation

base/timer/timer.cc

Index: base/timer/timer.cc
diff --git a/base/timer/timer.cc b/base/timer/timer.cc
index 31eec1bb574e83b32308dfbb3a94e335d550499c..d9f7b2459d7ff33e91adedd95e77eb34ac61f0c3 100644
--- a/base/timer/timer.cc
+++ b/base/timer/timer.cc
@@ -63,9 +63,6 @@ class BaseTimerTaskInternal {
   Timer* timer_;
 };
 
-Timer::Timer(bool retain_user_task, bool is_repeating)
-    : Timer(retain_user_task, is_repeating, nullptr) {}
-
 Timer::Timer(bool retain_user_task, bool is_repeating, TickClock* tick_clock)
     : scheduled_task_(nullptr),
       thread_id_(0),
@@ -77,12 +74,6 @@ Timer::Timer(bool retain_user_task, bool is_repeating, TickClock* tick_clock)
 Timer::Timer(const tracked_objects::Location& posted_from,
              TimeDelta delay,
              const base::Closure& user_task,
-             bool is_repeating)
-    : Timer(posted_from, delay, user_task, is_repeating, nullptr) {}
-
-Timer::Timer(const tracked_objects::Location& posted_from,
-             TimeDelta delay,
-             const base::Closure& user_task,
              bool is_repeating,
              TickClock* tick_clock)
     : scheduled_task_(nullptr),