cc: Use correct message loop proxy in BlockingTaskRunner

cc/trees/proxy.cc

Index: cc/trees/proxy.cc
diff --git a/cc/trees/proxy.cc b/cc/trees/proxy.cc
index 3136c65713f962c6049154c47ec98d61221f9e02..1d3c175dfddea0991e2032a96cb0b15f223ff6f8 100644
--- a/cc/trees/proxy.cc
+++ b/cc/trees/proxy.cc
@@ -6,6 +6,7 @@
 
 #include "base/message_loop/message_loop_proxy.h"
 #include "base/single_thread_task_runner.h"
+#include "cc/trees/blocking_task_runner.h"
 
 namespace cc {
 
@@ -69,18 +70,24 @@ void Proxy::SetMainThreadBlocked(bool is_main_thread_blocked) {
 Proxy::Proxy(scoped_refptr<base::SingleThreadTaskRunner> main_task_runner,
              scoped_refptr<base::SingleThreadTaskRunner> impl_task_runner)
 #if !DCHECK_IS_ON
-    : main_task_runner_(main_task_runner), impl_task_runner_(impl_task_runner) {
+    : main_task_runner_(main_task_runner),
+      impl_task_runner_(impl_task_runner),
+      blocking_main_thread_task_runner_(BlockingTaskRunner::current()) {
 #else
     : main_task_runner_(main_task_runner),
       impl_task_runner_(impl_task_runner),
+      blocking_main_thread_task_runner_(BlockingTaskRunner::current()),
       main_thread_id_(base::PlatformThread::CurrentId()),
       impl_thread_is_overridden_(false),
       is_main_thread_blocked_(false) {
 #endif
+  blocking_main_thread_task_runner_->SetTaskRunner(main_task_runner_);
 }
 
 Proxy::~Proxy() {
   DCHECK(IsMainThread());
+  blocking_main_thread_task_runner_->SetTaskRunner(
+      base::MessageLoopProxy::current());
 }
 
 }  // namespace cc