Don't do V8 GC on memory pressure notifications in visible renderers.

content/renderer/render_thread_impl.cc

Index: content/renderer/render_thread_impl.cc
diff --git a/content/renderer/render_thread_impl.cc b/content/renderer/render_thread_impl.cc
index 8a45ff89f8a7d597954e7406400353c9a92c62e7..a271f795ac44d538d67f0e8fd12d9213f524b132 100644
--- a/content/renderer/render_thread_impl.cc
+++ b/content/renderer/render_thread_impl.cc
@@ -2020,10 +2020,13 @@ void RenderThreadImpl::OnMemoryPressure(
       // Trigger full v8 garbage collection on memory pressure notifications.
       // This will potentially hang the renderer for a long time, however, when
       // we receive a memory pressure notification, we might be about to be
-      // killed.
-      blink::mainThreadIsolate()->LowMemoryNotification();
-      RenderThread::Get()->PostTaskToAllWebWorkers(
-          base::Bind(&LowMemoryNotificationOnThisThread));
+      // killed. Because of the janky hang don't do this to foreground
+      // renderers.
+      if (RendererIsHidden()) {
+        blink::mainThreadIsolate()->LowMemoryNotification();
+        RenderThread::Get()->PostTaskToAllWebWorkers(
+            base::Bind(&LowMemoryNotificationOnThisThread));
+      }
     }
 
     if (memory_pressure_level ==