UI resource are evicted when LTH is set to 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 1131050dc695a131dfee529af78852843b05ae7e..2763d33fbde49550b1dcc0cdb60f78e165ccbd13 100644
--- a/cc/trees/layer_tree_host_impl.cc
+++ b/cc/trees/layer_tree_host_impl.cc
@@ -200,7 +200,8 @@ 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_resources_evicted_(false) {
   DCHECK(proxy_->IsImplThread());
   DidVisibilityChange(this, visible_);
 
@@ -305,6 +306,14 @@ bool LayerTreeHostImpl::CanDraw() const {
         TRACE_EVENT_SCOPE_THREAD);
     return false;
   }
+
+  if (ui_resources_evicted_) {
+    TRACE_EVENT_INSTANT0(
+        "cc", "LayerTreeHostImpl::CanDraw ui resources evicted",
+        TRACE_EVENT_SCOPE_THREAD);
+    return false;
+  }
+
   return true;
 }
 
@@ -1536,11 +1545,16 @@ void LayerTreeHostImpl::SetVisible(bool visible) {
   DidVisibilityChange(this, visible_);
   EnforceManagedMemoryPolicy(ActualManagedMemoryPolicy());
 
-  // Evict tiles immediately if invisible since this tab may never get another
-  // draw or timer tick.
-  if (!visible_)
+  if (!visible_) {
+    // Evict tiles immediately if invisible since this tab may never get another
+    // draw or timer tick.
     ManageTiles();
 
+    // Evict UI resources
+    ui_resources_evicted_ = ui_resource_map_.size() > 0;
+    ReleaseUIResources();
+  }
+
   if (!renderer_)
     return;
 
@@ -1576,8 +1590,7 @@ void LayerTreeHostImpl::ReleaseTreeResources() {
   if (recycle_tree_ && recycle_tree_->root_layer())
     SendReleaseResourcesRecursive(recycle_tree_->root_layer());
 
-  // Remove all existing maps from UIResourceId to ResourceId.
-  ui_resource_map_.clear();
+  ReleaseUIResources();
 }
 
 void LayerTreeHostImpl::CreateAndSetRenderer(
@@ -2530,6 +2543,11 @@ void LayerTreeHostImpl::CreateUIResource(
                                 gfx::Rect(bitmap->GetSize()),
                                 gfx::Rect(bitmap->GetSize()),
                                 gfx::Vector2d(0, 0));
+
+  // Once any UI resource creation has been completed, we can assume that the
+  // evicted UI resources will have been recovered by the time CanDraw is
+  // checked.
+  ui_resources_evicted_ = false;
 }
 
 void LayerTreeHostImpl::DeleteUIResource(UIResourceId uid) {
@@ -2548,4 +2566,13 @@ ResourceProvider::ResourceId LayerTreeHostImpl::ResourceIdForUIResource(
   return 0;
 }
 
+void LayerTreeHostImpl::ReleaseUIResources() {
+  for (UIResourceMap::const_iterator iter = ui_resource_map_.begin();
+      iter != ui_resource_map_.end();
+      ++iter) {
+    resource_provider_->DeleteResource(iter->second);
+  }
+  ui_resource_map_.clear();
+}
+
 }  // namespace cc