Suppress another variant of the file util leak for heapcheck

tools/heapcheck/suppressions.txt

Index: tools/heapcheck/suppressions.txt
diff --git a/tools/heapcheck/suppressions.txt b/tools/heapcheck/suppressions.txt
index df5d88b878ff877fe6897d2d21a95544bdef116f..7e630761fce763947843723acb41d2372befa817 100644
--- a/tools/heapcheck/suppressions.txt
+++ b/tools/heapcheck/suppressions.txt
@@ -975,7 +975,7 @@
    fun:RenderViewTest_PageClickTracker_Test::TestBody
 }
 {
-   bug_56676
+   bug_56676_a
    Heapcheck:Leak
    fun:__gnu_cxx::new_allocator::allocate
    fun:std::_Vector_base::_M_allocate
@@ -984,3 +984,17 @@
    fun:MockDispatcher::DidReadDirectory
    fun:fileapi::FileSystemOperation::DidReadDirectory
 }
+{
+   bug_56676_b
+   Heapcheck:Leak
+   fun:__gnu_cxx::new_allocator::allocate
+   fun:std::string::_Rep::_S_create
+   fun:std::string::_S_construct
+   fun:std::string::_S_construct_aux
+   fun:std::string::_S_construct
+   fun:basic_string
+   fun:file_util::FileEnumerator::ReadDirectory
+   fun:file_util::FileEnumerator::Next
+   fun:::RelayReadDirectory::RunWork
+   fun:::MessageLoopRelay::ProcessOnTargetThread
+}