Use TimeTicks instead of clock() in gpu::CommandBufferHelper

gpu/command_buffer/client/cmd_buffer_helper.h

Index: gpu/command_buffer/client/cmd_buffer_helper.h
diff --git a/gpu/command_buffer/client/cmd_buffer_helper.h b/gpu/command_buffer/client/cmd_buffer_helper.h
index 86d3c3bf6c16d60a3915ce354ca84c7fc45dea98..c7c4c2ebd0df26b8abf521ab37d3c8818c3f7757 100644
--- a/gpu/command_buffer/client/cmd_buffer_helper.h
+++ b/gpu/command_buffer/client/cmd_buffer_helper.h
@@ -325,8 +325,9 @@ class GPU_EXPORT CommandBufferHelper {
   bool context_lost_;
   bool flush_automatically_;
 
-  // Using C runtime instead of base because this file cannot depend on base.
-  clock_t last_flush_time_;
+  // Using primitive type instead of base::TimeTicks because this file

[hamaji, 2014/07/09 06:03:15]

Is this comment right? It seems other header files in this directory #include
base headers.

For now, I declared this as int64 assuming this comment is right.

[piman, 2014/07/09 20:13:46]

This used to be true because of NaCl, but now it should be ok to depend on base
(we've been progressively fixing headers to that effect).

[hamaji, 2014/07/10 07:00:16]

Good news! Now I removed the comment and changed clock_t to TimeTicks.

+  // cannot depend on base.
+  int64 last_flush_time_;
 
   // Incremented every time the helper flushes the command buffer.
   // Can be used to track when prior commands have been flushed.