diff --git a/Source/WebKit2/ChangeLog b/Source/WebKit2/ChangeLog
index 557a5e8c6c85d698fe4dbb0029996ada9d8d0dc1..c2e9ae663e80c9ffd9c830b851cf79ae216e8709 100644
--- a/Source/WebKit2/ChangeLog
+++ b/Source/WebKit2/ChangeLog
@@ -1,3 +1,26 @@
+2011-05-02  Anders Carlsson  <andersca@apple.com>
+
+        Reviewed by Sam Weinig.
+
+        The web process locks up when the plug-in process crashes
+        https://bugs.webkit.org/show_bug.cgi?id=59999
+        <rdar://problem/8889303>
+
+        Add a hash map from plug-in paths to CoreIPC connections to PluginProcessConnectionManager.
+        Add PluginProcessConnectionManager::pluginProcessCrashed and make it look up the corresponding
+        CoreIPC connection and call postConnectionDidCloseOnConnectionWorkQueue on it.
+
+        * Platform/CoreIPC/Connection.cpp:
+        (CoreIPC::Connection::postConnectionDidCloseOnConnectionWorkQueue):
+        * Platform/CoreIPC/Connection.h:
+        * WebProcess/Plugins/PluginProcessConnectionManager.cpp:
+        (WebKit::PluginProcessConnectionManager::getPluginProcessConnection):
+        (WebKit::PluginProcessConnectionManager::removePluginProcessConnection):
+        (WebKit::PluginProcessConnectionManager::pluginProcessCrashed):
+        * WebProcess/Plugins/PluginProcessConnectionManager.h:
+        * WebProcess/WebProcess.cpp:
+        (WebKit::WebProcess::pluginProcessCrashed):
+
 2011-05-02  Anders Carlsson  <andersca@apple.com>
 
         Try to fix Windows build.
diff --git a/Source/WebKit2/Platform/CoreIPC/Connection.cpp b/Source/WebKit2/Platform/CoreIPC/Connection.cpp
index e9571e133d9e2879fa871ba9685e5c97c3542bcd..26b0d7c84279e1cfee21730bac1a8287cbbb1d9e 100644
--- a/Source/WebKit2/Platform/CoreIPC/Connection.cpp
+++ b/Source/WebKit2/Platform/CoreIPC/Connection.cpp
@@ -550,6 +550,11 @@ void Connection::processIncomingMessage(MessageID messageID, PassOwnPtr<Argument
     enqueueIncomingMessage(incomingMessage);
 }
 
+void Connection::postConnectionDidCloseOnConnectionWorkQueue()
+{
+    m_connectionQueue.scheduleWork(WorkItem::create(this, &Connection::connectionDidClose));
+}
+
 void Connection::connectionDidClose()
 {
     // The connection is now invalid.
diff --git a/Source/WebKit2/Platform/CoreIPC/Connection.h b/Source/WebKit2/Platform/CoreIPC/Connection.h
index 5969af2cd6c07e4fac4900af50b2d1b1b9a71578..cffbb4c63ad186cc32ac2becf87c7e94e1d94498 100644
--- a/Source/WebKit2/Platform/CoreIPC/Connection.h
+++ b/Source/WebKit2/Platform/CoreIPC/Connection.h
@@ -147,6 +147,8 @@ public:
 
     void setDefaultSyncMessageTimeout(double);
 
+    void postConnectionDidCloseOnConnectionWorkQueue();
+
     static const int DefaultTimeout = 0;
     static const int NoTimeout = -1;
 
diff --git a/Source/WebKit2/WebProcess/Plugins/PluginProcessConnectionManager.cpp b/Source/WebKit2/WebProcess/Plugins/PluginProcessConnectionManager.cpp
index faf78501da9e199d8f658db93581397943e70a01..31df5f222498013dd87feeeed6a136ed932bd296 100644
--- a/Source/WebKit2/WebProcess/Plugins/PluginProcessConnectionManager.cpp
+++ b/Source/WebKit2/WebProcess/Plugins/PluginProcessConnectionManager.cpp
@@ -75,6 +75,13 @@ PluginProcessConnection* PluginProcessConnectionManager::getPluginProcessConnect
     RefPtr<PluginProcessConnection> pluginProcessConnection = PluginProcessConnection::create(this, pluginPath, connectionIdentifier);
     m_pluginProcessConnections.append(pluginProcessConnection);
 
+    {
+        MutexLocker locker(m_pathsAndConnectionsMutex);
+        ASSERT(!m_pathsAndConnections.contains(pluginProcessConnection->pluginPath()));
+
+        m_pathsAndConnections.set(pluginPath, pluginProcessConnection->connection());
+    }
+
     return pluginProcessConnection.get();
 }
 
@@ -83,9 +90,29 @@ void PluginProcessConnectionManager::removePluginProcessConnection(PluginProcess
     size_t vectorIndex = m_pluginProcessConnections.find(pluginProcessConnection);
     ASSERT(vectorIndex != notFound);
 
+    {
+        MutexLocker locker(m_pathsAndConnectionsMutex);
+        ASSERT(m_pathsAndConnections.contains(pluginProcessConnection->pluginPath()));
+        
+        m_pathsAndConnections.remove(pluginProcessConnection->pluginPath());
+    }
+
     m_pluginProcessConnections.remove(vectorIndex);
 }
 
+void PluginProcessConnectionManager::pluginProcessCrashed(const String& pluginPath)
+{
+    MutexLocker locker(m_pathsAndConnectionsMutex);
+    CoreIPC::Connection* connection = m_pathsAndConnections.get(pluginPath).get();
+
+    // It's OK for connection to be null here; it will happen if this web process doesn't know
+    // anything about the plug-in process.
+    if (!connection)
+        return;
+
+    connection->postConnectionDidCloseOnConnectionWorkQueue();
+}
+
 } // namespace WebKit
 
 #endif // ENABLE(PLUGIN_PROCESS)
diff --git a/Source/WebKit2/WebProcess/Plugins/PluginProcessConnectionManager.h b/Source/WebKit2/WebProcess/Plugins/PluginProcessConnectionManager.h
index 86fa7e00ea77476e350dfe4de0f483a24000d250..45515cdf14d62b4c744212b37c02071780fe68ab 100644
--- a/Source/WebKit2/WebProcess/Plugins/PluginProcessConnectionManager.h
+++ b/Source/WebKit2/WebProcess/Plugins/PluginProcessConnectionManager.h
@@ -29,11 +29,18 @@
 #if ENABLE(PLUGIN_PROCESS)
 
 #include <wtf/Forward.h>
+#include <wtf/HashMap.h>
 #include <wtf/Noncopyable.h>
+#include <wtf/Threading.h>
 #include <wtf/Vector.h>
+#include <wtf/text/StringHash.h>
 
 // Manages plug-in process connections for the given web process.
 
+namespace CoreIPC {
+    class Connection;
+}
+
 namespace WebKit {
 
 class PluginProcessConnection;
@@ -47,8 +54,14 @@ public:
     PluginProcessConnection* getPluginProcessConnection(const String& pluginPath);
     void removePluginProcessConnection(PluginProcessConnection*);
 
+    // Called on the web process connection work queue.
+    void pluginProcessCrashed(const String& pluginPath);
+
 private:
     Vector<RefPtr<PluginProcessConnection> > m_pluginProcessConnections;
+
+    Mutex m_pathsAndConnectionsMutex;
+    HashMap<String, RefPtr<CoreIPC::Connection> > m_pathsAndConnections;
 };
 
 }
diff --git a/Source/WebKit2/WebProcess/WebProcess.cpp b/Source/WebKit2/WebProcess/WebProcess.cpp
index 1d316e3fe245f2c3119701b893e71727bd364150..f018f50827728d38716c35269256a30a8949394a 100644
--- a/Source/WebKit2/WebProcess/WebProcess.cpp
+++ b/Source/WebKit2/WebProcess/WebProcess.cpp
@@ -796,7 +796,7 @@ void WebProcess::clearPluginSiteData(const Vector<String>& pluginPaths, const Ve
 #if ENABLE(PLUGIN_PROCESS)
 void WebProcess::pluginProcessCrashed(const String& pluginPath)
 {
-    // FIXME: Implement.
+    m_pluginProcessConnectionManager.pluginProcessCrashed(pluginPath);
 }
 #endif