Add some traces for when render pass caching fails

cc/layer_tree_host_impl.cc

Index: cc/layer_tree_host_impl.cc
diff --git a/cc/layer_tree_host_impl.cc b/cc/layer_tree_host_impl.cc
index 89ebddeeb352afe939c941302827e0f38806e56a..19b996168fb844156c5de093e73060c533158f55 100644
--- a/cc/layer_tree_host_impl.cc
+++ b/cc/layer_tree_host_impl.cc
@@ -701,6 +701,13 @@ static void removeRenderPassesRecursive(RenderPass::Id removeRenderPassId, Layer
 
 bool LayerTreeHostImpl::CullRenderPassesWithCachedTextures::shouldRemoveRenderPass(const RenderPassDrawQuad& quad, const FrameData&) const
 {
+    if (!quad.contents_changed_since_last_frame.IsEmpty()) {
+        TRACE_EVENT0("cc", "CullRenderPassesWithCachedTextures have damage");

[danakj, 2012/12/14 23:21:13]

we could also early-out and return false in each of these if statements.

+    } else if (!m_renderer.haveCachedResourcesForRenderPassId(quad.render_pass_id)) {
+        TRACE_EVENT0("cc", "CullRenderPassesWithCachedTextures have no texture");
+    } else {
+        TRACE_EVENT0("cc", "CullRenderPassesWithCachedTextures dropped!");
+    }
     return quad.contents_changed_since_last_frame.IsEmpty() && m_renderer.haveCachedResourcesForRenderPassId(quad.render_pass_id);
 }