Pull in various gpu/command_buffer fixes from chromium

gpu/command_buffer/service/in_process_command_buffer.cc

Index: gpu/command_buffer/service/in_process_command_buffer.cc
diff --git a/gpu/command_buffer/service/in_process_command_buffer.cc b/gpu/command_buffer/service/in_process_command_buffer.cc
index c4fa167800478e1887431a4b14524413271e8053..65986f82540b9945fb79f2d626b319bbe4b5dbfb 100644
--- a/gpu/command_buffer/service/in_process_command_buffer.cc
+++ b/gpu/command_buffer/service/in_process_command_buffer.cc
@@ -124,7 +124,7 @@ base::LazyInstance<GpuInProcessThreadHolder> g_default_service =
 
 class ScopedEvent {
  public:
-  ScopedEvent(base::WaitableEvent* event) : event_(event) {}
+  explicit ScopedEvent(base::WaitableEvent* event) : event_(event) {}
   ~ScopedEvent() { event_->Signal(); }
 
  private: