Remove Compiler.depths parameter

This is no longer necessary with the depths array tracking and adds compiler overhead.

lib/handlebars/compiler/javascript-compiler.js

@@ -80,7 +80,7 @@ JavaScriptCompiler.prototype = {
 
     this.compileChildren(environment, options);
 
-    this.useDepths = this.useDepths || environment.depths.list.length || this.options.compat;
+    this.useDepths = this.useDepths || environment.useDepths || this.options.compat;
 
     var opcodes = environment.opcodes,
         opcode,
@@ -710,9 +710,7 @@ JavaScriptCompiler.prototype = {
 
   programExpression: function(guid) {
     var child = this.environment.children[guid],
-        depths = child.depths.list,
-        useDepths = this.useDepths,
-        depth;
+        useDepths = this.useDepths;
 
     var programParams = [child.index, 'data'];