cc: Split Proxy and TaskRunnerProvider for the LayerTreeHost

cc/trees/layer_tree_host_unittest_proxy.cc

Index: cc/trees/layer_tree_host_unittest_proxy.cc
diff --git a/cc/trees/layer_tree_host_unittest_proxy.cc b/cc/trees/layer_tree_host_unittest_proxy.cc
index 370760e0cf687409dee84f5152c163ee5603d5ec..78545ef2adafc82a5d3412e7be4c7602ae5b654d 100644
--- a/cc/trees/layer_tree_host_unittest_proxy.cc
+++ b/cc/trees/layer_tree_host_unittest_proxy.cc
@@ -84,14 +84,16 @@ class ThreadProxyTest : public ProxyTest {
   }
 
   const ThreadProxy::MainThreadOnly& ThreadProxyMainOnly() const {
+    DCHECK(task_runner_provider());
+    DCHECK(task_runner_provider()->HasImplThread());
     DCHECK(proxy());
-    DCHECK(proxy()->HasImplThread());
     return static_cast<const ThreadProxy*>(proxy())->main();
   }
 
   const ThreadProxy::CompositorThreadOnly& ThreadProxyImplOnly() const {
+    DCHECK(task_runner_provider());
+    DCHECK(task_runner_provider()->HasImplThread());
     DCHECK(proxy());
-    DCHECK(proxy()->HasImplThread());
     return static_cast<const ThreadProxy*>(proxy())->impl();
   }