Use per-frame task runner at GpuBenchmarking::input_injector_

V8 should not be executed on per-thread task runner. Use per-frame (per-
execution-context) task runner instead.

Bug: 870606
Change-Id: Ibaf9e02bb33eacbf0f29b2bb30645ad8d7a19121
Reviewed-on: https://chromium-review.googlesource.com/c/1331291Reviewed-by: Kenneth Russell <kbr@chromium.org>
Commit-Queue: Hajime Hoshi <hajimehoshi@chromium.org>
Cr-Commit-Position: refs/heads/master@{#607487}

content/renderer/gpu/gpu_benchmarking_extension.cc

@@ -528,8 +528,9 @@ GpuBenchmarking::~GpuBenchmarking() {
 
 void GpuBenchmarking::EnsureRemoteInterface() {
   if (!input_injector_) {
-    render_frame_->GetRemoteInterfaces()->GetInterface(
-        mojo::MakeRequest(&input_injector_));
+    render_frame_->GetRemoteInterfaces()->GetInterface(mojo::MakeRequest(
+        &input_injector_,
+        render_frame_->GetTaskRunner(blink::TaskType::kInternalDefault)));
   }
 }