Restore comments about reentrancy in the HostDispatcher::Send function

BUG=none
TEST=none
Review URL: http://codereview.chromium.org/8095021

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@103598 0039d316-1c4b-4281-b951-d872f2087c98

1 files changed, 7 insertions, 1 deletions

diff --git a/ppapi/proxy/host_dispatcher.cc b/ppapi/proxy/host_dispatcher.cc
index 26a1c15..91a3759 100644
--- a/ppapi/proxy/host_dispatcher.cc
+++ b/ppapi/proxy/host_dispatcher.cc
@@ -137,9 +137,15 @@ bool HostDispatcher::Send(IPC::Message* msg) {
   // Prevent the dispatcher from going away during the call. Scenarios
   // where this could happen include a Send for a sync message which while
   // waiting for the reply, dispatches an incoming ExecuteScript call which
-  // destroys the plugin module and in turn the dispatcher,
+  // destroys the plugin module and in turn the dispatcher.
   ScopedModuleReference ref(this);
 
+  // Normal sync messages are set to unblock, which would normally cause the
+  // plugin to be reentered to process them. We only want to do this when we
+  // know the plugin is in a state to accept reentrancy. Since the plugin side
+  // never clears this flag on messages it sends, we can't get deadlock, but we
+  // may still get reentrancy in the host as a result.
+
   if (!allow_plugin_reentrancy_)
     msg->set_unblock(false);
   return Dispatcher::Send(msg);