diff --git a/dom/plugins/ipc/PluginHangUIParent.cpp b/dom/plugins/ipc/PluginHangUIParent.cpp
index 94166506046..0277d93e8ba 100644
--- a/dom/plugins/ipc/PluginHangUIParent.cpp
+++ b/dom/plugins/ipc/PluginHangUIParent.cpp
@@ -68,12 +68,12 @@ private:
 namespace mozilla {
 namespace plugins {
 
-const DWORD PluginHangUIParent::kTimeout = 30000U;
-
 PluginHangUIParent::PluginHangUIParent(PluginModuleParent* aModule,
-                                       const int32_t aHangUITimeoutPref)
+                                       const int32_t aHangUITimeoutPref,
+                                       const int32_t aChildTimeoutPref)
   : mModule(aModule),
     mTimeoutPrefMs(static_cast<uint32_t>(aHangUITimeoutPref) * 1000U),
+    mIPCTimeoutMs(static_cast<uint32_t>(aChildTimeoutPref) * 1000U),
     mMainThreadMessageLoop(MessageLoop::current()),
     mIsShowing(false),
     mLastUserResponse(0),
@@ -129,7 +129,7 @@ PluginHangUIParent::Init(const nsString& aPluginName)
   }
 
   nsresult rv;
-  rv = mMiniShm.Init(this, ::IsDebuggerPresent() ? INFINITE : kTimeout);
+  rv = mMiniShm.Init(this, ::IsDebuggerPresent() ? INFINITE : mIPCTimeoutMs);
   NS_ENSURE_SUCCESS(rv, false);
   nsCOMPtr<nsIProperties>
     directoryService(do_GetService(NS_DIRECTORY_SERVICE_CONTRACTID));
@@ -210,6 +210,10 @@ PluginHangUIParent::Init(const nsString& aPluginName)
     commandLine.AppendLooseValue(L"-");
   }
 
+  nsAutoString ipcTimeoutStr;
+  ipcTimeoutStr.AppendInt(mIPCTimeoutMs);
+  commandLine.AppendLooseValue(ipcTimeoutStr.get());
+
   std::wstring ipcCookie;
   rv = mMiniShm.GetCookie(ipcCookie);
   if (NS_FAILED(rv)) {
@@ -245,7 +249,7 @@ PluginHangUIParent::Init(const nsString& aPluginName)
                                   INFINITE,
                                   WT_EXECUTEDEFAULT | WT_EXECUTEONLYONCE);
     ::WaitForSingleObject(mShowEvent, ::IsDebuggerPresent() ? INFINITE
-                                                            : kTimeout);
+                                                            : mIPCTimeoutMs);
     // Setting this to true even if we time out on mShowEvent. This timeout 
     // typically occurs when the machine is thrashing so badly that 
     // plugin-hang-ui.exe is taking a while to start. If we didn't set 
@@ -269,7 +273,6 @@ VOID CALLBACK PluginHangUIParent::SOnHangUIProcessExit(PVOID aContext,
     // If plugin-hang-ui.exe was unexpectedly terminated, we need to re-enable.
     ::EnableWindow(object->mMainWindowHandle, TRUE);
   }
-  object->mMiniShm.CleanUp();
 }
 
 bool
diff --git a/dom/plugins/ipc/PluginHangUIParent.h b/dom/plugins/ipc/PluginHangUIParent.h
index 935dab1dfc4..2069ef52a38 100644
--- a/dom/plugins/ipc/PluginHangUIParent.h
+++ b/dom/plugins/ipc/PluginHangUIParent.h
@@ -35,7 +35,8 @@ class PluginHangUIParent : public MiniShmObserver
 {
 public:
   PluginHangUIParent(PluginModuleParent* aModule,
-                     const int32_t aHangUITimeoutPref);
+                     const int32_t aHangUITimeoutPref,
+                     const int32_t aChildTimeoutPref);
   virtual ~PluginHangUIParent();
 
   /**
@@ -131,6 +132,7 @@ private:
 private:
   PluginModuleParent* mModule;
   const uint32_t mTimeoutPrefMs;
+  const uint32_t mIPCTimeoutMs;
   MessageLoop* mMainThreadMessageLoop;
   volatile bool mIsShowing;
   unsigned int mLastUserResponse;
@@ -142,8 +144,6 @@ private:
   DWORD mResponseTicks;
   MiniShmParent mMiniShm;
 
-  static const DWORD kTimeout;
-
   DISALLOW_COPY_AND_ASSIGN(PluginHangUIParent);
 };
 
diff --git a/dom/plugins/ipc/PluginModuleParent.cpp b/dom/plugins/ipc/PluginModuleParent.cpp
index d87eb8b3ca7..732558693a0 100755
--- a/dom/plugins/ipc/PluginModuleParent.cpp
+++ b/dom/plugins/ipc/PluginModuleParent.cpp
@@ -566,7 +566,8 @@ PluginModuleParent::LaunchHangUI()
         mHangUIParent = nullptr;
     }
     mHangUIParent = new PluginHangUIParent(this, 
-            Preferences::GetInt(kHangUITimeoutPref, 0));
+            Preferences::GetInt(kHangUITimeoutPref, 0),
+            Preferences::GetInt(kChildTimeoutPref, 0));
     nsAutoString pluginName;
     if (!GetPluginName(pluginName)) {
         return false;
diff --git a/dom/plugins/ipc/hangui/PluginHangUIChild.cpp b/dom/plugins/ipc/hangui/PluginHangUIChild.cpp
index 98128bb3ffe..eee2ffd7550 100644
--- a/dom/plugins/ipc/hangui/PluginHangUIChild.cpp
+++ b/dom/plugins/ipc/hangui/PluginHangUIChild.cpp
@@ -37,8 +37,6 @@ typedef std::vector<WinInfo> WinInfoVec;
 
 PluginHangUIChild* PluginHangUIChild::sSelf = nullptr;
 const int PluginHangUIChild::kExpectedMinimumArgc = 10;
-const DWORD PluginHangUIChild::kProcessTimeout = 1200000U;
-const DWORD PluginHangUIChild::kShmTimeout = 5000U;
 
 PluginHangUIChild::PluginHangUIChild()
   : mResponseBits(0),
@@ -46,7 +44,8 @@ PluginHangUIChild::PluginHangUIChild()
     mDlgHandle(NULL),
     mMainThread(NULL),
     mParentProcess(NULL),
-    mRegWaitProcess(NULL)
+    mRegWaitProcess(NULL),
+    mIPCTimeoutMs(0)
 {
 }
 
@@ -98,10 +97,15 @@ PluginHangUIChild::Init(int aArgc, wchar_t* aArgv[])
       FreeLibrary(shell32);
     }
   }
+  std::wistringstream issTimeout(aArgv[++i]);
+  issTimeout >> mIPCTimeoutMs;
+  if (!issTimeout) {
+    return false;
+  }
 
   nsresult rv = mMiniShm.Init(this,
                               std::wstring(aArgv[++i]),
-                              IsDebuggerPresent() ? INFINITE : kShmTimeout);
+                              IsDebuggerPresent() ? INFINITE : mIPCTimeoutMs);
   if (NS_FAILED(rv)) {
     return false;
   }
@@ -374,7 +378,7 @@ PluginHangUIChild::WaitForDismissal()
     return false;
   }
   DWORD waitResult = WaitForSingleObjectEx(mParentProcess,
-                                           kProcessTimeout,
+                                           mIPCTimeoutMs,
                                            TRUE);
   return waitResult == WAIT_OBJECT_0 ||
          waitResult == WAIT_IO_COMPLETION;
diff --git a/dom/plugins/ipc/hangui/PluginHangUIChild.h b/dom/plugins/ipc/hangui/PluginHangUIChild.h
index aaee2e82f82..50d546f2638 100644
--- a/dom/plugins/ipc/hangui/PluginHangUIChild.h
+++ b/dom/plugins/ipc/hangui/PluginHangUIChild.h
@@ -96,11 +96,10 @@ private:
   HANDLE mMainThread;
   HANDLE mParentProcess;
   HANDLE mRegWaitProcess;
+  DWORD mIPCTimeoutMs;
   MiniShmChild mMiniShm;
 
   static const int kExpectedMinimumArgc;
-  static const DWORD kProcessTimeout;
-  static const DWORD kShmTimeout;
 
   typedef HRESULT (WINAPI *SETAPPUSERMODELID)(PCWSTR);