Add support for tagging layers.

cc/layer.cc

Index: cc/layer.cc
diff --git a/cc/layer.cc b/cc/layer.cc
index 28cff9864bd9642365b933fc5b8ae7c6ed2a6ce5..4e6c6727980b3c4fb0b3836ae2564552d5f52e9e 100644
--- a/cc/layer.cc
+++ b/cc/layer.cc
@@ -58,6 +58,7 @@ Layer::Layer()
     , m_boundsContainPageScale(false)
     , m_layerAnimationDelegate(0)
     , m_layerScrollClient(0)
+    , m_tags(kTagNone)
 {
     if (m_layerId < 0) {
         s_nextLayerId = 1;
@@ -846,6 +847,26 @@ ScrollbarLayer* Layer::toScrollbarLayer()
     return 0;
 }
 
+void Layer::setTags(unsigned int tags)
+{
+    m_tags = tags;
+}
+
+unsigned int Layer::getTags() const
+{
+    return m_tags;
+}
+
+void Layer::addTag(Tag tag)
+{
+    m_tags |= tag;
+}
+
+bool Layer::getTag(Tag tag) const
+{
+    return m_tags & tag;
+}
+
 void sortLayers(std::vector<scoped_refptr<Layer> >::iterator, std::vector<scoped_refptr<Layer> >::iterator, void*)
 {
     // Currently we don't use z-order to decide what to paint, so there's no need to actually sort Layers.