cc: Fix lost context handling when using impl-side painting.

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 e6b9ac99e0d49ae673f001b56a4ce6ad514d74aa..39ef4829134910bc1fd967ece7edb66895ae8a72 100644
--- a/cc/layer_tree_host_impl.cc
+++ b/cc/layer_tree_host_impl.cc
@@ -966,10 +966,13 @@ bool LayerTreeHostImpl::initializeRenderer(scoped_ptr<OutputSurface> outputSurfa
     // Since we will create a new resource provider, we cannot continue to use
     // the old resources (i.e. renderSurfaces and texture IDs). Clear them
     // before we destroy the old resource provider.
-    if (rootLayer()) {
+    if (rootLayer())
         clearRenderSurfaces();
-        sendDidLoseOutputSurfaceRecursive(rootLayer());
-    }
+    if (activeTree()->RootLayer())
+        sendDidLoseOutputSurfaceRecursive(activeTree()->RootLayer());
+    if (pendingTree() && pendingTree()->RootLayer())
+        sendDidLoseOutputSurfaceRecursive(pendingTree()->RootLayer());
+
     // Note: order is important here.
     m_renderer.reset();
     m_tileManager.reset();