Fixing a problem, where a hung renderer process is not killed when navigating away

content/browser/renderer_host/render_widget_host_unittest.cc

 // Copyright (c) 2012 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "base/basictypes.h"
 #include "base/memory/scoped_ptr.h"
 #include "base/shared_memory.h"
 #include "base/timer.h"
 #include "content/browser/browser_thread_impl.h"
 #include "content/browser/renderer_host/backing_store.h"
@@ skipping 752 matching lines @@
   EXPECT_FALSE(host_->unresponsive_timer_fired());
   host_->StartHangMonitorTimeout(TimeDelta::FromMilliseconds(10));
 
   // Wait long enough for first timeout and see if it fired.
   MessageLoop::current()->PostDelayedTask(
       FROM_HERE, MessageLoop::QuitClosure(), TimeDelta::FromMilliseconds(40));
   MessageLoop::current()->Run();
   EXPECT_TRUE(host_->unresponsive_timer_fired());
 }
 
+// Test that the hang monitor timer expires properly if it is started, then
+// updated to a shorter duration.
+TEST_F(RenderWidgetHostTest, ShorterDelayHangMonitorTimeout) {
+  // Start with a timeout.
+  host_->StartHangMonitorTimeout(TimeDelta::FromMilliseconds(100));
+
+  // Start it again with shorter delay.
+  EXPECT_FALSE(host_->unresponsive_timer_fired());
+  host_->StartHangMonitorTimeout(TimeDelta::FromMilliseconds(20));
+
+  // Wait long enough for first timeout and see if it fired.
+  MessageLoop::current()->PostDelayedTask(
+      FROM_HERE, MessageLoop::QuitClosure(), TimeDelta::FromMilliseconds(25));
+  MessageLoop::current()->Run();
+  EXPECT_TRUE(host_->unresponsive_timer_fired());
+}
+
 // Test that the hang monitor catches two input events but only one ack.
 // This can happen if the second input event causes the renderer to hang.
 // This test will catch a regression of crbug.com/111185.
 TEST_F(RenderWidgetHostTest, MultipleInputEvents) {
   // Configure the host to wait 10ms before considering
   // the renderer hung.
   host_->set_hung_renderer_delay_ms(10);
 
   // Send two events but only one ack.
   SimulateKeyboardEvent(WebInputEvent::RawKeyDown);
   SimulateKeyboardEvent(WebInputEvent::RawKeyDown);
   SendInputEventACK(WebInputEvent::RawKeyDown, true);
 
   // Wait long enough for first timeout and see if it fired.
   MessageLoop::current()->PostDelayedTask(
       FROM_HERE, MessageLoop::QuitClosure(), TimeDelta::FromMilliseconds(40));
   MessageLoop::current()->Run();
   EXPECT_TRUE(host_->unresponsive_timer_fired());
 }