[cc] Evict UIResources when the renderer is not visible

cc/trees/layer_tree_host_impl.cc

Index: cc/trees/layer_tree_host_impl.cc
diff --git a/cc/trees/layer_tree_host_impl.cc b/cc/trees/layer_tree_host_impl.cc
index 08e4ac16366b7a4e3b1de129cd5b81d1c7a994d1..d6bebf57d3aee896ec46a59f346844b3e9d8bb47 100644
--- a/cc/trees/layer_tree_host_impl.cc
+++ b/cc/trees/layer_tree_host_impl.cc
@@ -201,7 +201,8 @@ LayerTreeHostImpl::LayerTreeHostImpl(
       external_stencil_test_enabled_(false),
       animation_registrar_(AnimationRegistrar::Create()),
       rendering_stats_instrumentation_(rendering_stats_instrumentation),
-      need_to_update_visible_tiles_before_draw_(false) {
+      need_to_update_visible_tiles_before_draw_(false),
+      ui_resource_eviction_count_(0) {
   DCHECK(proxy_->IsImplThread());
   DidVisibilityChange(this, visible_);
 
@@ -311,6 +312,13 @@ bool LayerTreeHostImpl::CanDraw() const {
         TRACE_EVENT_SCOPE_THREAD);
     return false;
   }
+  if (active_tree_->ui_resource_eviction_count_recreated() !=
+      ui_resource_eviction_count()) {
+    TRACE_EVENT_INSTANT0(
+        "cc", "LayerTreeHostImpl::CanDraw UI resources evicted not recreated",
+        TRACE_EVENT_SCOPE_THREAD);
+    return false;
+  }
   return true;
 }
 
@@ -1558,6 +1566,9 @@ void LayerTreeHostImpl::SetVisible(bool visible) {
   DidVisibilityChange(this, visible_);
   EnforceManagedMemoryPolicy(ActualManagedMemoryPolicy());
 
+  if (!visible_)
+    DeleteAllUIResources();
+
   // Evict tiles immediately if invisible since this tab may never get another
   // draw or timer tick.
   if (!visible_)
@@ -2639,12 +2650,20 @@ void LayerTreeHostImpl::DeleteUIResource(UIResourceId uid) {
 }
 
 void LayerTreeHostImpl::DeleteAllUIResources() {
+  if (ui_resource_map_.empty())
+    return;
+
   for (UIResourceMap::const_iterator iter = ui_resource_map_.begin();
       iter != ui_resource_map_.end();
       ++iter) {
     resource_provider_->DeleteResource(iter->second);
   }
   ui_resource_map_.clear();
+
+  ui_resource_eviction_count_ += 1;
+  client_->SetNeedsCommitOnImplThread();
+  client_->OnCanDrawStateChanged(CanDraw());
+  client_->RenewTreePriority();

[powei, 2013/09/09 20:34:25]

Maybe a stupid question, but what's the purpose of calling this method?  Is
there an implicit contract that says priority should be updated when CanDraw
changes?

[ccameron, 2013/09/09 21:01:16]

Oops! I needed to update RenewTreePriority to "prefer new content" when this
happens... that way we'll switch to the new tree (with all its UI resources).
Without that change, this did nothing...

 }
 
 ResourceProvider::ResourceId LayerTreeHostImpl::ResourceIdForUIResource(