bind-gen: Fix SymbolDefinitionNode insertion to be aware of registeration

Make SymbolDefinitionNode insertion happen only when the SymbolNode
is already registered.

Bug: 839389
Change-Id: I5ce1e21511866a511659d1d6e7b3658ccddc5650
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1873807Reviewed-by: Hitoshi Yoshida <peria@chromium.org>
Commit-Queue: Yuki Shiino <yukishiino@chromium.org>
Cr-Commit-Position: refs/heads/master@{#708944}

third_party/blink/renderer/bindings/scripts/bind_gen/code_node.py

@@ -281,6 +281,15 @@ class CodeNode(object):
             return self.upstream.is_code_symbol_defined(symbol_node)
         return False
 
+    def is_code_symbol_registered(self, symbol_node):
+        """
+        Returns True if |symbol_node| is registered and available for use at
+        this point.  See also |SymbolScopeNode.register_code_symbol|.
+        """
+        if self.outer is not None:
+            return self.outer.is_code_symbol_registered(symbol_node)
+        return False
+
     def on_undefined_code_symbol_found(self, symbol_node):
         """Receives a report of use of an undefined symbol node."""
         assert isinstance(symbol_node, SymbolNode)
@@ -532,13 +541,16 @@ class SymbolScopeNode(SequenceNode):
             separator_last="\n",
             renderer=renderer)
 
+        self._registered_code_symbols = set()
+
     def _render(self, renderer, last_render_state):
         # Sort nodes in order to render reproducible results.
         symbol_nodes = sorted(
             last_render_state.undefined_code_symbols,
             key=lambda symbol_node: symbol_node.name)
         for symbol_node in symbol_nodes:
-            if not self.is_code_symbol_defined(symbol_node):
+            if (self.is_code_symbol_registered(symbol_node)
+                    and not self.is_code_symbol_defined(symbol_node)):
                 self._insert_symbol_definition(symbol_node)
 
         return super(SymbolScopeNode, self)._render(
@@ -605,10 +617,17 @@ class SymbolScopeNode(SequenceNode):
         did_insert = insert_right_before_first_use(self)
         assert did_insert
 
+    def is_code_symbol_registered(self, symbol_node):
+        if symbol_node in self._registered_code_symbols:
+            return True
+        return super(SymbolScopeNode,
+                     self).is_code_symbol_registered(symbol_node)
+
     def register_code_symbol(self, symbol_node):
         """Registers a SymbolNode and makes it available in this scope."""
         assert isinstance(symbol_node, SymbolNode)
         self.add_template_var(symbol_node.name, symbol_node)
+        self._registered_code_symbols.add(symbol_node)
 
     def register_code_symbols(self, symbol_nodes):
         for symbol_node in symbol_nodes: