Prevent hang monitor restarts when hidden

content/browser/renderer_host/render_widget_host_unittest.cc

Index: content/browser/renderer_host/render_widget_host_unittest.cc
diff --git a/content/browser/renderer_host/render_widget_host_unittest.cc b/content/browser/renderer_host/render_widget_host_unittest.cc
index ea9d84e52cccbaf196b8c3849cd4229fe65f0c15..7d23c00c4d814f4e409747b8133158a095604f1e 100644
--- a/content/browser/renderer_host/render_widget_host_unittest.cc
+++ b/content/browser/renderer_host/render_widget_host_unittest.cc
@@ -992,6 +992,43 @@ TEST_F(RenderWidgetHostTest, ShorterDelayHangMonitorTimeout) {
   EXPECT_TRUE(host_->unresponsive_timer_fired());
 }
 
+// Test that the hang monitor timer is effectively disabled when the widget is
+// hidden.
+TEST_F(RenderWidgetHostTest, HangMonitorTimeoutDisabledWhenHidden) {
+  host_->StartHangMonitorTimeout(TimeDelta::FromMicroseconds(1));
+
+  // Hiding the widget should deactivate the timeout.
+  host_->WasHidden();
+
+  // The timeout should not fire.
+  EXPECT_FALSE(host_->unresponsive_timer_fired());
+  base::MessageLoop::current()->PostDelayedTask(
+      FROM_HERE,
+      base::MessageLoop::QuitClosure(),
+      TimeDelta::FromMicroseconds(2));
+  base::MessageLoop::current()->Run();
+  EXPECT_FALSE(host_->unresponsive_timer_fired());
+
+  // The timeout should never reactivate while hidden.
+  host_->StartHangMonitorTimeout(TimeDelta::FromMicroseconds(1));
+  base::MessageLoop::current()->PostDelayedTask(
+      FROM_HERE,
+      base::MessageLoop::QuitClosure(),
+      TimeDelta::FromMicroseconds(2));
+  base::MessageLoop::current()->Run();
+  EXPECT_FALSE(host_->unresponsive_timer_fired());
+
+  // Showing the widget should restore normal timeout behavior.
+  host_->WasShown(ui::LatencyInfo());
+  host_->StartHangMonitorTimeout(TimeDelta::FromMicroseconds(1));
+  base::MessageLoop::current()->PostDelayedTask(
+      FROM_HERE,
+      base::MessageLoop::QuitClosure(),
+      TimeDelta::FromMicroseconds(2));
+  base::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.