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

chrome/renderer/render_widget.cc

Index: chrome/renderer/render_widget.cc
===================================================================
--- chrome/renderer/render_widget.cc	(revision 24223)
+++ chrome/renderer/render_widget.cc	(working copy)
@@ -180,8 +180,10 @@
   closing_ = true;
 
   // Browser correspondence is no longer needed at this point.
-  if (routing_id_ != MSG_ROUTING_NONE)
+  if (routing_id_ != MSG_ROUTING_NONE) {
     render_thread_->RemoveRoute(routing_id_);
+    SetHidden(false);
+  }
 
   // If there is a Send call on the stack, then it could be dangerous to close
   // now.  Post a task that only gets invoked when there are no nested message
@@ -203,7 +205,7 @@
   resizer_rect_ = resizer_rect;
 
   // TODO(darin): We should not need to reset this here.
-  is_hidden_ = false;
+  SetHidden(false);
   needs_repainting_on_restore_ = false;
 
   // We shouldn't be asked to resize to our current size.
@@ -232,7 +234,7 @@
 
 void RenderWidget::OnWasHidden() {
   // Go into a mode where we stop generating paint and scrolling events.
-  is_hidden_ = true;
+  SetHidden(true);
 }
 
 void RenderWidget::OnWasRestored(bool needs_repainting) {
@@ -241,7 +243,7 @@
     return;
 
   // See OnWasHidden
-  is_hidden_ = false;
+  SetHidden(false);
 
   if (!needs_repainting && !needs_repainting_on_restore_)
     return;
@@ -736,6 +738,18 @@
   webwidget_->setTextDirection(direction);
 }
 
+void RenderWidget::SetHidden(bool hidden) {
+  if (is_hidden_ == hidden)
+    return;
+
+  // The status has changed.  Tell the RenderThread about it.
+  is_hidden_ = hidden;
+  if (is_hidden_)
+    render_thread_->WidgetHidden();
+  else
+    render_thread_->WidgetRestored();
+}
+
 void RenderWidget::SetBackground(const SkBitmap& background) {
   background_ = background;
   // Generate a full repaint.