Wait for URLBlacklist update tasks on automation tests.

content/browser/browser_thread.cc

Index: content/browser/browser_thread.cc
diff --git a/content/browser/browser_thread.cc b/content/browser/browser_thread.cc
index c3b400540e8d8897a68ea7cccccd4340f4b65908..84fa13b8cfe5470273d55ef84cee285a8b1de4fb 100644
--- a/content/browser/browser_thread.cc
+++ b/content/browser/browser_thread.cc
@@ -7,6 +7,7 @@
 #include "base/bind.h"
 #include "base/message_loop.h"
 #include "base/message_loop_proxy.h"
+#include "base/synchronization/waitable_event.h"
 #include "base/threading/thread_restrictions.h"
 
 // Friendly names for the well-known threads.
@@ -252,6 +253,22 @@ bool BrowserThread::GetCurrentThreadIdentifier(ID* identifier) {
 }
 
 // static
+bool BrowserThread::WaitForPendingTasksOn(ID identifier) {
+  // Avoid deadlocking self.
+  if (CurrentlyOn(identifier))
+    return false;
+  base::WaitableEvent event(true   /* manual reset */,
+                            false  /* not initially signaled */);
+  if (!PostTask(identifier,
+                FROM_HERE,
+                base::Bind(&base::WaitableEvent::Signal,
+                           base::Unretained(&event))))
+    return false;
+  event.Wait();
+  return true;
+}
+
+// static
 scoped_refptr<base::MessageLoopProxy>
 BrowserThread::GetMessageLoopProxyForThread(
     ID identifier) {