Revert of Reland: Lazily initialize MessageLoop for faster thread startup

base/threading/thread.h

Index: base/threading/thread.h
diff --git a/base/threading/thread.h b/base/threading/thread.h
index 6b2f1c5169a7685bd8c5084ed4faa583bb73fbe3..49156063929759f62cab534432251947df10dec8 100644
--- a/base/threading/thread.h
+++ b/base/threading/thread.h
@@ -13,13 +13,11 @@
 #include "base/message_loop/message_loop.h"
 #include "base/message_loop/timer_slack.h"
 #include "base/single_thread_task_runner.h"
-#include "base/synchronization/lock.h"
 #include "base/threading/platform_thread.h"
 
 namespace base {
 
 class MessagePump;
-class WaitableEvent;
 
 // A simple thread abstraction that establishes a MessageLoop on a new thread.
 // The consumer uses the MessageLoop of the thread to cause code to execute on
@@ -47,7 +45,7 @@
     // This is ignored if message_pump_factory.is_null() is false.
     MessageLoop::Type message_loop_type;
 
-    // Specifies timer slack for thread message loop.
+    // Specify timer slack for thread message loop.
     TimerSlack timer_slack;
 
     // Used to create the MessagePump for the MessageLoop. The callback is Run()
@@ -83,7 +81,7 @@
   // init_com_with_mta(false) and then StartWithOptions() with any message loop
   // type other than TYPE_UI.
   void init_com_with_mta(bool use_mta) {
-    DCHECK(!start_event_);
+    DCHECK(!started_);
     com_status_ = use_mta ? MTA : STA;
   }
 #endif
@@ -104,18 +102,6 @@
   // i.e. during a DllMain, global object construction or destruction, atexit()
   // callback.
   bool StartWithOptions(const Options& options);
-
-  // Starts the thread and wait for the thread to start and run initialization
-  // before returning. It's same as calling Start() and then
-  // WaitUntilThreadStarted().
-  // Note that using this (instead of Start() or StartWithOptions() causes
-  // jank on the calling thread, should be used only in testing code.
-  bool StartAndWaitForTesting();
-
-  // Blocks until the thread starts running. Called within StartAndWait().
-  // Note that calling this causes jank on the calling thread, must be used
-  // carefully for production code.
-  bool WaitUntilThreadStarted();
 
   // Signals the thread to exit and returns once the thread has exited.  After
   // this method returns, the Thread object is completely reset and may be used
@@ -180,7 +166,7 @@
   PlatformThreadHandle thread_handle() { return thread_; }
 
   // The thread ID.
-  PlatformThreadId thread_id() const;
+  PlatformThreadId thread_id() const { return thread_id_; }
 
   // Returns true if the thread has been started, and not yet stopped.
   bool IsRunning() const;
@@ -222,32 +208,33 @@
   ComStatus com_status_;
 #endif
 
+  // Whether we successfully started the thread.
+  bool started_;
+
   // If true, we're in the middle of stopping, and shouldn't access
   // |message_loop_|. It may non-NULL and invalid.
   bool stopping_;
 
   // True while inside of Run().
   bool running_;
-  mutable base::Lock running_lock_;  // Protects running_.
+
+  // Used to pass data to ThreadMain.
+  struct StartupData;
+  StartupData* startup_data_;
 
   // The thread's handle.
   PlatformThreadHandle thread_;
-  mutable base::Lock thread_lock_;  // Protects thread_.
 
   // The thread's message loop.  Valid only while the thread is alive.  Set
   // by the created thread.
   MessageLoop* message_loop_;
 
-  // Stores Options::timer_slack_ until the message loop has been bound to
-  // a thread.
-  TimerSlack message_loop_timer_slack_;
+  // Our thread's ID.
+  PlatformThreadId thread_id_;
 
   // The name of the thread.  Used for debugging purposes.
   std::string name_;
 
-  // Non-null if the thread has successfully started.
-  scoped_ptr<WaitableEvent> start_event_;
-
   friend void ThreadQuitHelper();
 
   DISALLOW_COPY_AND_ASSIGN(Thread);