Expose public interface for composited selection bounds

public/platform/WebLayerTreeView.h

Index: public/platform/WebLayerTreeView.h
diff --git a/public/platform/WebLayerTreeView.h b/public/platform/WebLayerTreeView.h
index 134201641833257cbdaed29ace3b3bf55091f46e..8ad7a4efca4d2974d59fcf5bafabeb4310fa178a 100644
--- a/public/platform/WebLayerTreeView.h
+++ b/public/platform/WebLayerTreeView.h
@@ -42,6 +42,7 @@ class WebLayer;
 struct WebPoint;
 struct WebRect;
 struct WebRenderingStats;
+struct WebSelectionBound;
 
 class WebLayerTreeView {
 public:
@@ -125,6 +126,13 @@ public:
         const WebLayer* outerViewportScrollLayer) { }
     virtual void clearViewportLayers() { }
 
+    // Used to update the active selection bounds.
+    // If the (empty) selection is an insertion point, |anchor| and |focus| will be identical with type |Caret|.
+    // If the (non-empty) selection has mixed RTL/LTR text, |anchor| and |focus| may share the same type,
+    // |SelectionLeft| or |SelectionRight|.
+    virtual void registerSelection(const WebSelectionBound& anchor, const WebSelectionBound& focus) { }
+    virtual void clearSelection() { }
+
     // Debugging / dangerous ---------------------------------------------
 
     // Toggles the FPS counter in the HUD layer