Update Linux to use scoped_refptr<T>::get() rather than implicit "operator T*"

cc/trees/layer_tree_host.cc

Index: cc/trees/layer_tree_host.cc
diff --git a/cc/trees/layer_tree_host.cc b/cc/trees/layer_tree_host.cc
index e86aaf52c90c93e291f97892e21e90965a09fffd..3d97f15ce843e3d94262ca95f3fe0480d16d312b 100644
--- a/cc/trees/layer_tree_host.cc
+++ b/cc/trees/layer_tree_host.cc
@@ -107,7 +107,7 @@ LayerTreeHost::LayerTreeHost(LayerTreeHostClient* client,
 
 bool LayerTreeHost::Initialize(
     scoped_refptr<base::SingleThreadTaskRunner> impl_task_runner) {
-  if (impl_task_runner)
+  if (impl_task_runner.get())
     return InitializeProxy(ThreadProxy::Create(this, impl_task_runner));
   else
     return InitializeProxy(SingleThreadProxy::Create(this));