plugins: use OnChannelError to detect when the channel goes away

Previously we used a special Watcher object to watch the process,
but that is not portable to POSIX and this is simpler anyway.
With this change, I now see ~PluginProcessHost() running when a
plugin crashes.

If you recall all the way back to
  http://codereview.chromium.org/16814
we did a similar thing to the renderer host.

Review URL: http://codereview.chromium.org/155331

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@20414 0039d316-1c4b-4281-b951-d872f2087c98

2 files changed, 13 insertions, 31 deletions

diff --git a/chrome/common/child_process_host.cc b/chrome/common/child_process_host.cc
index c2c925e..67d9a5a 100644
--- a/chrome/common/child_process_host.cc
+++ b/chrome/common/child_process_host.cc
@@ -51,8 +51,7 @@ ChildProcessHost::ChildProcessHost(
     : Receiver(type),
       ALLOW_THIS_IN_INITIALIZER_LIST(listener_(this)),
       resource_dispatcher_host_(resource_dispatcher_host),
-      opening_channel_(false),
-      process_event_(NULL) {
+      opening_channel_(false) {
   Singleton<ChildProcessList>::get()->push_back(this);
 }
 
@@ -62,16 +61,8 @@ ChildProcessHost::~ChildProcessHost() {
 
   resource_dispatcher_host_->CancelRequestsForProcess(GetProcessId());
 
-  if (handle()) {
-    watcher_.StopWatching();
+  if (handle())
     ProcessWatcher::EnsureProcessTerminated(handle());
-
-#if defined(OS_WIN)
-    // Above call took ownership, so don't want WaitableEvent to assert because
-    // the handle isn't valid anymore.
-    process_event_->Release();
-#endif
-  }
 }
 
 bool ChildProcessHost::CreateChannel() {
@@ -87,13 +78,8 @@ bool ChildProcessHost::CreateChannel() {
 }
 
 void ChildProcessHost::SetHandle(base::ProcessHandle process) {
-#if defined(OS_WIN)
-  process_event_.reset(new base::WaitableEvent(process));
-
   DCHECK(!handle());
   set_handle(process);
-  watcher_.StartWatching(process_event_.get(), this);
-#endif
 }
 
 void ChildProcessHost::InstanceCreated() {
@@ -113,20 +99,20 @@ void ChildProcessHost::Notify(NotificationType type) {
       FROM_HERE, new ChildNotificationTask(type, this));
 }
 
-void ChildProcessHost::OnWaitableEventSignaled(base::WaitableEvent *event) {
-#if defined(OS_WIN)
-  HANDLE object = event->handle();
+void ChildProcessHost::OnChildDied() {
   DCHECK(handle());
-  DCHECK_EQ(object, handle());
 
-  bool did_crash = base::DidProcessCrash(NULL, object);
+  bool did_crash = base::DidProcessCrash(NULL, handle());
   if (did_crash) {
     // Report that this child process crashed.
     Notify(NotificationType::CHILD_PROCESS_CRASHED);
   }
   // Notify in the main loop of the disconnection.
   Notify(NotificationType::CHILD_PROCESS_HOST_DISCONNECTED);
-#endif
+
+  // On POSIX, once we've called DidProcessCrash, handle() is no longer
+  // valid.  Ensure the destructor doesn't try to use it.
+  set_handle(NULL);
 
   delete this;
 }
@@ -185,6 +171,9 @@ void ChildProcessHost::ListenerHook::OnChannelConnected(int32 peer_pid) {
 void ChildProcessHost::ListenerHook::OnChannelError() {
   host_->opening_channel_ = false;
   host_->OnChannelError();
+
+  // This will delete host_, which will also destroy this!
+  host_->OnChildDied();
 }
 
 
diff --git a/chrome/common/child_process_host.h b/chrome/common/child_process_host.h
index caabe66..3b97200 100644
--- a/chrome/common/child_process_host.h
+++ b/chrome/common/child_process_host.h
@@ -10,7 +10,6 @@
 
 #include "base/basictypes.h"
 #include "base/scoped_ptr.h"
-#include "base/waitable_event_watcher.h"
 #include "chrome/browser/renderer_host/resource_dispatcher_host.h"
 #include "chrome/common/ipc_channel.h"
 
@@ -19,7 +18,6 @@ class NotificationType;
 // Plugins/workers and other child processes that live on the IO thread should
 // derive from this class.
 class ChildProcessHost : public ResourceDispatcherHost::Receiver,
-                         public base::WaitableEventWatcher::Delegate,
                          public IPC::Channel::Listener {
  public:
   virtual ~ChildProcessHost();
@@ -78,8 +76,8 @@ class ChildProcessHost : public ResourceDispatcherHost::Receiver,
   // Sends the given notification to the notification service on the UI thread.
   void Notify(NotificationType type);
 
-  // WaitableEventWatcher::Delegate implementation:
-  virtual void OnWaitableEventSignaled(base::WaitableEvent *event);
+  // Called when the child process goes away.
+  void OnChildDied();
 
   // By using an internal class as the IPC::Channel::Listener, we can intercept
   // OnMessageReceived/OnChannelConnected and do our own processing before
@@ -106,11 +104,6 @@ class ChildProcessHost : public ResourceDispatcherHost::Receiver,
 
   // IPC Channel's id.
   std::string channel_id_;
-
-  // Used to watch the child process handle.
-  base::WaitableEventWatcher watcher_;
-
-  scoped_ptr<base::WaitableEvent> process_event_;
 };
 
 #endif  // CHROME_COMMON_CHILD_PROCESS_HOST_H_