Schedule idle handler in the foreground tab based on CPU usage and user activity.

content/test/mock_render_thread.cc

Index: content/test/mock_render_thread.cc
diff --git a/content/test/mock_render_thread.cc b/content/test/mock_render_thread.cc
index eca409e1e333fb699a7567b90bed5ab8a3a53f8d..15ab64da9932e186f9aa312dcd5c8e09c8751815 100644
--- a/content/test/mock_render_thread.cc
+++ b/content/test/mock_render_thread.cc
@@ -141,6 +141,9 @@ void MockRenderThread::SetIdleNotificationDelayInMs(
     int64 idle_notification_delay_in_ms) {
 }
 
+void MockRenderThread::PostponeIdleNotification() {
+}
+
 #if defined(OS_WIN)
 void MockRenderThread::PreCacheFont(const LOGFONT& log_font) {
 }