Disallow UI/IO thread blocking on any other thread.

base/threading/simple_thread.cc

Index: base/threading/simple_thread.cc
===================================================================
--- base/threading/simple_thread.cc	(revision 133458)
+++ base/threading/simple_thread.cc	(working copy)
@@ -6,6 +6,7 @@
 
 #include "base/logging.h"
 #include "base/threading/platform_thread.h"
+#include "base/threading/thread_restrictions.h"
 #include "base/string_number_conversions.h"
 
 namespace base {
@@ -30,6 +31,7 @@
   DCHECK(!HasBeenStarted()) << "Tried to Start a thread multiple times.";
   bool success = PlatformThread::Create(options_.stack_size(), this, &thread_);
   DCHECK(success);
+  base::ThreadRestrictions::ScopedAllowWait allow_wait;
   event_.Wait();  // Wait for the thread to complete initialization.
 }
 
@@ -40,6 +42,11 @@
   joined_ = true;
 }
 
+bool SimpleThread::HasBeenStarted() {
+  base::ThreadRestrictions::ScopedAllowWait allow_wait;
+  return event_.IsSignaled();
+}
+
 void SimpleThread::ThreadMain() {
   tid_ = PlatformThread::CurrentId();
   // Construct our full name of the form "name_prefix_/TID".