content: Add command line flag for native GPU memory buffers.

content/renderer/render_thread_impl.cc

Index: content/renderer/render_thread_impl.cc
diff --git a/content/renderer/render_thread_impl.cc b/content/renderer/render_thread_impl.cc
index 43f10b2aabb4d2980c8620144f945fa9687fe8c6..316cfe32e69b6564c086bdccfd61958fee280d6d 100644
--- a/content/renderer/render_thread_impl.cc
+++ b/content/renderer/render_thread_impl.cc
@@ -520,6 +520,8 @@ void RenderThreadImpl::Init() {
   is_one_copy_enabled_ = !command_line.HasSwitch(switches::kDisableOneCopy);
 #endif
 
+  use_image_external_ = command_line.HasSwitch(switches::kUseImageExternal);
+
   if (command_line.HasSwitch(switches::kDisableLCDText)) {
     is_lcd_text_enabled_ = false;
   } else if (command_line.HasSwitch(switches::kEnableLCDText)) {