Revert of Add thread checking to RunLoop, deprecate MessageLoopRunner.

base/run_loop.cc

Index: base/run_loop.cc
diff --git a/base/run_loop.cc b/base/run_loop.cc
index 6faaeee2ba323d505e1d2ad09490455953e5b3c4..a2322f849582c3b22cc78b9c9980b3fd8a1a92b8 100644
--- a/base/run_loop.cc
+++ b/base/run_loop.cc
@@ -25,7 +25,6 @@
 }
 
 void RunLoop::Run() {
-  DCHECK(thread_checker_.CalledOnValidThread());
   if (!BeforeRun())
     return;
 
@@ -45,7 +44,6 @@
 }
 
 void RunLoop::Quit() {
-  DCHECK(thread_checker_.CalledOnValidThread());
   quit_called_ = true;
   if (running_ && loop_->run_loop_ == this) {
     // This is the inner-most RunLoop, so quit now.
@@ -54,7 +52,6 @@
 }
 
 void RunLoop::QuitWhenIdle() {
-  DCHECK(thread_checker_.CalledOnValidThread());
   quit_when_idle_received_ = true;
 }