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

content/renderer/render_thread_impl.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 "content/renderer/render_thread_impl.h"
 
 #include <algorithm>
 #include <limits>
 #include <map>
 #include <utility>
@@ skipping 2002 matching lines @@
 
   // Do not call into blink if it is not initialized.
   if (blink_platform_impl_) {
     blink::WebMemoryPressureListener::onMemoryPressure(
         static_cast<blink::WebMemoryPressureLevel>(memory_pressure_level));
 
     if (blink::mainThreadIsolate()) {
       // 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 ==
         base::MemoryPressureListener::MEMORY_PRESSURE_LEVEL_CRITICAL) {
       // Purge Skia font cache, by setting it to 0 and then again to the
       // previous limit.
       size_t font_cache_limit = SkGraphics::SetFontCacheLimit(0);
       SkGraphics::SetFontCacheLimit(font_cache_limit);
     }
   }
@@ skipping 137 matching lines @@
 }
 
 void RenderThreadImpl::PendingRenderFrameConnect::OnConnectionError() {
   size_t erased =
       RenderThreadImpl::current()->pending_render_frame_connects_.erase(
           routing_id_);
   DCHECK_EQ(1u, erased);
 }
 
 }  // namespace content