Modify the RenderThread to track the number of widgets...

chrome/renderer/render_thread.cc

Index: chrome/renderer/render_thread.cc
===================================================================
--- chrome/renderer/render_thread.cc	(revision 24223)
+++ chrome/renderer/render_thread.cc	(working copy)
@@ -9,6 +9,7 @@
 
 #include "base/command_line.h"
 #include "base/lazy_instance.h"
+#include "base/logging.h"
 #include "base/shared_memory.h"
 #include "base/stats_table.h"
 #include "base/thread_local.h"
@@ -58,6 +59,8 @@
 
 namespace {
 static const unsigned int kCacheStatsDelayMS = 2000 /* milliseconds */;
+static const double kInitialIdleHandlerDelayS = 1.0 /* seconds */;
+
 static base::LazyInstance<base::ThreadLocalPointer<RenderThread> > lazy_tls(
     base::LINKER_INITIALIZED);
 
@@ -105,8 +108,11 @@
 #endif
 
   plugin_refresh_allowed_ = true;
-  cache_stats_factory_.reset(
-      new ScopedRunnableMethodFactory<RenderThread>(this));
+  cache_stats_task_pending_ = false;
+  widget_count_ = 0;
+  hidden_widget_count_ = 0;
+  idle_notification_delay_in_s_ = kInitialIdleHandlerDelayS;
+  task_factory_.reset(new ScopedRunnableMethodFactory<RenderThread>(this));
 
   visited_link_slave_.reset(new VisitedLinkSlave());
   user_script_slave_.reset(new UserScriptSlave());
@@ -156,6 +162,30 @@
   channel()->RemoveFilter(filter);
 }
 
+void RenderThread::WidgetHidden() {
+  DCHECK(hidden_widget_count_ <= widget_count_);
+  hidden_widget_count_++ ;
+  if (hidden_widget_count_ == widget_count_) {
+    // Reset the delay.
+    idle_notification_delay_in_s_ = kInitialIdleHandlerDelayS;
+
+    // Schedule the IdleHandler to wakeup in a bit.
+    MessageLoop::current()->PostDelayedTask(FROM_HERE,
+        task_factory_->NewRunnableMethod(&RenderThread::IdleHandler),
+        static_cast<int64>(floor(idle_notification_delay_in_s_)) * 1000);
+  }
+}
+
+void RenderThread::WidgetRestored() {
+  DCHECK(hidden_widget_count_ > 0);
+  hidden_widget_count_--;
+
+  // Note: we may have a timer pending to call the IdleHandler (see the
+  // WidgetHidden() code).  But we don't bother to cancel it as it is
+  // benign and won't do anything if the tab is un-hidden when it is
+  // called.
+}
+
 void RenderThread::Resolve(const char* name, size_t length) {
   return dns_master_->Resolve(name, length);
 }
@@ -316,15 +346,17 @@
   WebCache::UsageStats stats;
   WebCache::getUsageStats(&stats);
   Send(new ViewHostMsg_UpdatedCacheStats(stats));
+  cache_stats_task_pending_ = false;
 }
 
 void RenderThread::InformHostOfCacheStatsLater() {
   // Rate limit informing the host of our cache stats.
-  if (!cache_stats_factory_->empty())
+  if (cache_stats_task_pending_)
     return;
 
+  cache_stats_task_pending_ = true;
   MessageLoop::current()->PostDelayedTask(FROM_HERE,
-      cache_stats_factory_->NewRunnableMethod(
+      task_factory_->NewRunnableMethod(
           &RenderThread::InformHostOfCacheStats),
       kCacheStatsDelayMS);
 }
@@ -417,6 +449,31 @@
     WebKit::enableMediaPlayer();
 }
 
+void RenderThread::IdleHandler() {
+  // It is possible that the timer was set while the widgets were idle,
+  // but that they are no longer idle.  If so, just return.
+  if (hidden_widget_count_ < widget_count_)
+    return;
+
+  LOG(INFO) << "RenderThread calling v8 IdleNotification for " << this;
+
+  // When V8::IdleNotification returns true, it means that it has cleaned up
+  // as much as it can.  There is no point in continuing to call it.
+  if (!v8::V8::IdleNotification(false)) {
+    // Dampen the delay using the algorithm:
+    //    delay = delay + 1 / (delay + 2)
+    // Using floor(delay) has a dampening effect such as:
+    //    1s, 1, 1, 2, 2, 2, 2, 3, 3, ...
+    idle_notification_delay_in_s_ +=
+        1.0 / (idle_notification_delay_in_s_ + 2.0);
+
+    // Schedule the next timer.
+    MessageLoop::current()->PostDelayedTask(FROM_HERE,
+        task_factory_->NewRunnableMethod(&RenderThread::IdleHandler),
+        static_cast<int64>(floor(idle_notification_delay_in_s_)) * 1000);
+  }
+}
+
 void RenderThread::OnExtensionMessageInvoke(const std::string& function_name,
                                             const ListValue& args) {
   RendererExtensionBindings::Invoke(function_name, args, NULL);