Revert of cc: Add a main thread LayerListIterator

cc/trees/layer_tree_host.h

Index: cc/trees/layer_tree_host.h
diff --git a/cc/trees/layer_tree_host.h b/cc/trees/layer_tree_host.h
index 6d3ffde52500ded84edbdf7129b363cc9bd14602..0573db3a70289fb00b0feaaf6f6cd814a7391ccf 100644
--- a/cc/trees/layer_tree_host.h
+++ b/cc/trees/layer_tree_host.h
@@ -31,7 +31,6 @@
 #include "cc/input/scrollbar.h"
 #include "cc/input/top_controls_state.h"
 #include "cc/layers/layer_collections.h"
-#include "cc/layers/layer_list_iterator.h"
 #include "cc/output/output_surface.h"
 #include "cc/output/renderer_capabilities.h"
 #include "cc/output/swap_promise.h"
@@ -147,11 +146,6 @@
   void DidCommitAndDrawFrame() { client_->DidCommitAndDrawFrame(); }
   void DidCompleteSwapBuffers() { client_->DidCompleteSwapBuffers(); }
   bool UpdateLayers();
-
-  LayerListIterator<Layer> begin();
-  LayerListIterator<Layer> end();
-  LayerListReverseIterator<Layer> rbegin();
-  LayerListReverseIterator<Layer> rend();
 
   // Called when the compositor completed page scale animation.
   void DidCompletePageScaleAnimation();