Disallow UI/IO thread blocking on any other thread.

base/threading/thread_restrictions.cc

Index: base/threading/thread_restrictions.cc
===================================================================
--- base/threading/thread_restrictions.cc	(revision 133458)
+++ base/threading/thread_restrictions.cc	(working copy)
@@ -21,6 +21,9 @@
 LazyInstance<ThreadLocalBoolean>::Leaky
     g_singleton_disallowed = LAZY_INSTANCE_INITIALIZER;
 
+LazyInstance<ThreadLocalBoolean>::Leaky
+    g_wait_disallowed = LAZY_INSTANCE_INITIALIZER;
+
 }  // anonymous namespace
 
 // static
@@ -42,6 +45,7 @@
   }
 }
 
+// static
 bool ThreadRestrictions::SetSingletonAllowed(bool allowed) {
   bool previous_disallowed = g_singleton_disallowed.Get().Get();
   g_singleton_disallowed.Get().Set(!allowed);
@@ -58,6 +62,25 @@
   }
 }
 
+// static
+void ThreadRestrictions::DisallowWaiting() {
+  g_wait_disallowed.Get().Set(true);
+}
+
+// static
+void ThreadRestrictions::AssertWaitAllowed() {
+  if (g_wait_disallowed.Get().Get()) {
+    LOG(FATAL) << "Waiting is not allowed to be used on this thread to prevent"
+               << "jank and deadlock.";
+  }
+}
+
+bool ThreadRestrictions::SetWaitAllowed(bool allowed) {
+  bool previous_disallowed = g_wait_disallowed.Get().Get();
+  g_wait_disallowed.Get().Set(!allowed);
+  return !previous_disallowed;
+}
+
 }  // namespace base
 
 #endif  // NDEBUG