Suppress extensions leak on Mac.

tools/valgrind/memcheck/suppressions.txt

Index: tools/valgrind/memcheck/suppressions.txt
diff --git a/tools/valgrind/memcheck/suppressions.txt b/tools/valgrind/memcheck/suppressions.txt
index 24b104d1f75724016a83e1e3a4f7da038ddf2a2c..5b1c266092a053e7bae68e7c0f42713aef225933 100644
--- a/tools/valgrind/memcheck/suppressions.txt
+++ b/tools/valgrind/memcheck/suppressions.txt
@@ -2700,3 +2700,29 @@
    fun:_ZN11MessageLoop11RunInternalEv
    fun:_ZN11MessageLoop10RunHandlerEv
 }
+{
+   bug_42880
+   Memcheck:Leak
+   fun:_Znw*
+   fun:_ZN9__gnu_cxx13new_allocatorISt13_Rb_tree_nodeISt4pairIKSsSt3setIiSt4lessIiESaIiEEEEE8allocateEmPKv
+   fun:_ZNSt8_Rb_treeISsSt4pairIKSsSt3setIiSt4lessIiESaIiEEESt10_Select1stIS7_ES3_ISsESaIS7_EE11_M_get_nodeEv
+   fun:_ZNSt8_Rb_treeISsSt4pairIKSsSt3setIiSt4lessIiESaIiEEESt10_Select1stIS7_ES3_ISsESaIS7_EE14_M_create_nodeERKS7_
+   fun:_ZNSt8_Rb_treeISsSt4pairIKSsSt3setIiSt4lessIiESaIiEEESt10_Select1stIS7_ES3_ISsESaIS7_EE9_M_insertEPSt18_Rb_tree_node_baseSE_RKS7_
+   fun:_ZNSt8_Rb_treeISsSt4pairIKSsSt3setIiSt4lessIiESaIiEEESt10_Select1stIS7_ES3_ISsESaIS7_EE13insert_uniqueERKS7_
+   fun:_ZNSt8_Rb_treeISsSt4pairIKSsSt3setIiSt4lessIiESaIiEEESt10_Select1stIS7_ES3_ISsESaIS7_EE13insert_uniqueESt17_Rb_tree_iteratorIS7_ERKS7_
+   fun:_ZNSt3mapISsSt3setIiSt4lessIiESaIiEES1_ISsESaISt4pairIKSsS4_EEE6insertESt17_Rb_tree_iteratorIS8_ERKS8_
+   fun:_ZNSt3mapISsSt3setIiSt4lessIiESaIiEES1_ISsESaISt4pairIKSsS4_EEEixERS7_
+   fun:_ZN23ExtensionMessageService24DispatchEventToRenderersERKSsS1_bRK4GURL
+   fun:_ZL13DispatchEventP7ProfilePKcSs
+   fun:_ZN27ExtensionBrowserEventRouter12TabClosingAtEP11TabContentsi
+   fun:_ZN13TabStripModel16InternalCloseTabEP11TabContentsib
+   fun:_ZN13TabStripModel17InternalCloseTabsESt6vectorIiSaIiEEb
+   fun:_ZN13TabStripModel12CloseAllTabsEv
+   fun:_ZN7Browser12CloseAllTabsEv
+   fun:_ZN7Browser15OnWindowClosingEv
+   fun:-[BrowserWindowController windowShouldClose:]
+   fun:-[NSWindow _document:shouldClose:contextInfo:]
+   fun:-[NSWindow __close]
+   fun:-[NSWindow _close:]
+   fun:-[NSApplication sendAction:to:from:]
+}