Pinch/Zoom Infrastructure & Plumbing CL

cc/test/layer_tree_json_parser.cc

Index: cc/test/layer_tree_json_parser.cc
diff --git a/cc/test/layer_tree_json_parser.cc b/cc/test/layer_tree_json_parser.cc
index 9a1b198a7b772d423d50c56adde28aee44e974e8..ffd4568acd929121844047d53161e52d4bfb8bfb 100644
--- a/cc/test/layer_tree_json_parser.cc
+++ b/cc/test/layer_tree_json_parser.cc
@@ -101,8 +101,23 @@ scoped_refptr<Layer> ParseTreeFromValue(base::Value* val,
     new_layer->SetContentsOpaque(contents_opaque);
 
   bool scrollable;
+  // TODO(wjmaclean) At some time in the future we may wish to test that a

[enne (OOO), 2013/11/14 22:59:01]

This is pretty unfortunate.  Can you file a bug to fix this up and link to it in
a comment here?  I'm ok with punting on fixing up all of the json and adjusting
the reader to handle this for this patch, but I think this hack shouldn't live.

[wjmaclean, 2013/12/24 21:03:49]

Indeed, this hack was never meant to live ;-)

I'll file the bug and link it here.

+  // reconstructed layer tree contains the correct linkage for the scroll
+  // clip layer. This is complicated by the fact that the json output doesn't
+  // (currently) re-construct the tree with the same layer IDs as the original.
+  // But, since a clip layer is always an ancestor of the scrollable layer, we
+  // can just count the number of upwards hops to the clip layer and write that
+  // into the json file (with 0 hops implying no clip layer, i.e. not
+  // scrollable). Reconstructing the tree can then be accomplished by passing
+  // the parent pointer to this function and traversing the same number of
+  // ancestors to determine the pointer to the clip layer. The LayerTreesMatch()
+  // function should then check that both original and reconstructed layers
+  // have the same positioning with respect to their clip layers.
+  //
+  // For now, we can safely indicate a layer is scrollable by giving it a
+  // pointer to itself, something not normally allowed in a working tree.
   if (dict->GetBoolean("Scrollable", &scrollable))
-    new_layer->SetScrollable(scrollable);
+    new_layer->SetScrollable(scrollable ? new_layer.get() : NULL);
 
   bool wheel_handler;
   if (dict->GetBoolean("WheelHandler", &wheel_handler))