Add webgl constants back to correct class

tools/dom/scripts/htmldartgenerator.py

Index: tools/dom/scripts/htmldartgenerator.py
diff --git a/tools/dom/scripts/htmldartgenerator.py b/tools/dom/scripts/htmldartgenerator.py
index 29b757f9d84bfbdecdf0dfa24c00b98f2e61f62f..607a75694feea0721187eb46b693b24762cf9037 100644
--- a/tools/dom/scripts/htmldartgenerator.py
+++ b/tools/dom/scripts/htmldartgenerator.py
@@ -107,11 +107,28 @@ class HtmlDartGenerator(object):
           convert_to_future_members):
         self.AddOperation(ConvertToFuture(info), declare_only)
 
+  def _HoistableConstants(self, interface):
+    consts = []
+    if interface.parents:
+      for parent in interface.parents:
+        parent_interface = self._database.GetInterface(parent.type.id)
+        # TODO(vsm): This should be a general check.  E.g., on private
+        # interfaces?
+        if parent.type.id == 'WebGLRenderingContextBase':
+          consts = consts + parent_interface.constants
+    return consts
+
   def AddSecondaryMembers(self, interface):
     # With multiple inheritance, attributes and operations of non-first
     # interfaces need to be added.  Sometimes the attribute or operation is
     # defined in the current interface as well as a parent.  In that case we
     # avoid making a duplicate definition and pray that the signatures match.
+    if not self._renamer.ShouldSuppressInterface(interface):
+      secondary_constants = sorted(self._HoistableConstants(interface),
+                                     ConstantOutputOrder)
+      for const in secondary_constants:
+        self.AddConstant(const)
+
     secondary_parents = self._database.TransitiveSecondaryParents(interface,
                           not self._dart_use_blink)
     for parent_interface in sorted(secondary_parents):