Flush SimpleCache worker pool between all tests.

content/browser/browser_thread_impl.cc

Index: content/browser/browser_thread_impl.cc
diff --git a/content/browser/browser_thread_impl.cc b/content/browser/browser_thread_impl.cc
index 641056ffb7869b7d3f4019d3b1f6388d1fc48f00..1c9799a2dea04abc208b3f5a6680f0ac5860aac3 100644
--- a/content/browser/browser_thread_impl.cc
+++ b/content/browser/browser_thread_impl.cc
@@ -15,6 +15,7 @@
 #include "base/threading/sequenced_worker_pool.h"
 #include "base/threading/thread_restrictions.h"
 #include "content/public/browser/browser_thread_delegate.h"
+#include "net/disk_cache/simple/simple_backend_impl.h"
 
 #if defined(OS_ANDROID)
 #include "base/android/jni_android.h"
@@ -146,6 +147,7 @@ void BrowserThreadImpl::FlushThreadPoolHelper() {
   if (g_globals == NULL)
     return;
   g_globals.Get().blocking_pool->FlushForTesting();
+  disk_cache::SimpleBackendImpl::FlushWorkerPoolForTesting();
 }
 
 void BrowserThreadImpl::Init() {