Add OrderingBarrierCHROMIUM API.

gpu/command_buffer/client/cmd_buffer_helper.cc

Index: gpu/command_buffer/client/cmd_buffer_helper.cc
diff --git a/gpu/command_buffer/client/cmd_buffer_helper.cc b/gpu/command_buffer/client/cmd_buffer_helper.cc
index a99201e4b36164ef01ef218d7651f6fe55e851b9..c67f434f3bfa31602eccccf1ad0c98a473cd0efb 100644
--- a/gpu/command_buffer/client/cmd_buffer_helper.cc
+++ b/gpu/command_buffer/client/cmd_buffer_helper.cc
@@ -23,6 +23,7 @@ CommandBufferHelper::CommandBufferHelper(CommandBuffer* command_buffer)
       token_(0),
       put_(0),
       last_put_sent_(0),
+      last_shallow_put_sent_(0),
 #if defined(CMD_HELPER_PERIODIC_FLUSH_CHECK)
       commands_issued_(0),
 #endif
@@ -153,12 +154,26 @@ void CommandBufferHelper::Flush() {
   if (usable() && last_put_sent_ != put_) {
     last_flush_time_ = base::TimeTicks::Now();
     last_put_sent_ = put_;
+    last_shallow_put_sent_ = put_;
     command_buffer_->Flush(put_);
     ++flush_generation_;
     CalcImmediateEntries(0);
   }
 }
 
+void CommandBufferHelper::ShallowFlush() {
+  // Wrap put_ before flush.
+  if (put_ == total_entry_count_)
+    put_ = 0;
+
+  if (usable() && last_shallow_put_sent_ != put_) {
+    last_shallow_put_sent_ = put_;
+    command_buffer_->ShallowFlush(put_);
+    ++flush_generation_;
+    CalcImmediateEntries(0);
+  }
+}
+
 #if defined(CMD_HELPER_PERIODIC_FLUSH_CHECK)
 void CommandBufferHelper::PeriodicFlushCheck() {
   base::TimeTicks current_time = base::TimeTicks::Now();