cc: Fix resource eviction with impl-side painting.

cc/layer_tree_impl.cc

Index: cc/layer_tree_impl.cc
diff --git a/cc/layer_tree_impl.cc b/cc/layer_tree_impl.cc
index 769639a4091c9dc2e987c7c7b546658329f23489..ad2298184324f45482c9b33c20012e6d2427c869 100644
--- a/cc/layer_tree_impl.cc
+++ b/cc/layer_tree_impl.cc
@@ -19,7 +19,8 @@ LayerTreeImpl::LayerTreeImpl(LayerTreeHostImpl* layer_tree_host_impl)
     , currently_scrolling_layer_(0)
     , background_color_(0)
     , has_transparent_background_(false)
-    , scrolling_layer_id_from_previous_tree_(0) {
+    , scrolling_layer_id_from_previous_tree_(0)
+    , contents_textures_purged_(false) {
 }
 
 LayerTreeImpl::~LayerTreeImpl() {
@@ -215,6 +216,20 @@ void LayerTreeImpl::DidBecomeActive() {
     DidBecomeActiveRecursive(RootLayer());
 }
 
+bool LayerTreeImpl::ContentsTexturesPurged() const {
+  return contents_textures_purged_;
+}
+
+void LayerTreeImpl::SetContentsTexturesPurged() {
+  contents_textures_purged_ = true;
+  layer_tree_host_impl_->OnCanDrawStateChangedForTree(this);
+}
+
+void LayerTreeImpl::ResetContentsTexturesPurged() {
+  contents_textures_purged_ = false;
+  layer_tree_host_impl_->OnCanDrawStateChangedForTree(this);
+}
+
 const LayerTreeSettings& LayerTreeImpl::settings() const {
   return layer_tree_host_impl_->settings();
 }