[bindings] Implement an ExperimentEnabled IDL extended attribute.

third_party/WebKit/Source/bindings/scripts/v8_utilities.py

Index: third_party/WebKit/Source/bindings/scripts/v8_utilities.py
diff --git a/third_party/WebKit/Source/bindings/scripts/v8_utilities.py b/third_party/WebKit/Source/bindings/scripts/v8_utilities.py
index cb770bb9492051f5897afb10dd0e83c8c1c585f9..151e1891495e27bf37c67bed300395cdb28f96e8 100644
--- a/third_party/WebKit/Source/bindings/scripts/v8_utilities.py
+++ b/third_party/WebKit/Source/bindings/scripts/v8_utilities.py
@@ -380,6 +380,29 @@ def measure_as(definition_or_member, interface):
     return None
 
 
+def runtime_feature_name(definition_or_member):
+    extended_attributes = definition_or_member.extended_attributes
+    if 'RuntimeEnabled' not in extended_attributes:
+        return None
+    return extended_attributes['RuntimeEnabled']
+
+
+def is_api_experiment_enabled(definition_or_member):
+    return 'APIExperimentEnabled' in definition_or_member.extended_attributes
+
+
+def api_experiment_name(definition_or_member):
+    return definition_or_member.extended_attributes['APIExperimentEnabled'] if is_api_experiment_enabled(definition_or_member) else None
+
+
+def api_experiment_enabled_function(definition_or_member):
+    experiment_name = api_experiment_name(definition_or_member)
+    feature_name = runtime_feature_name(definition_or_member)
+    if not feature_name or not experiment_name:
+        return
+    return 'ExperimentalFeatures::%sEnabled' % uncapitalize(feature_name)
+
+
 # [RuntimeEnabled]
 def runtime_enabled_function_name(definition_or_member):
     """Returns the name of the RuntimeEnabledFeatures function.
@@ -388,10 +411,16 @@ def runtime_enabled_function_name(definition_or_member):
     Given extended attribute RuntimeEnabled=FeatureName, return:
         RuntimeEnabledFeatures::{featureName}Enabled
     """
-    extended_attributes = definition_or_member.extended_attributes
-    if 'RuntimeEnabled' not in extended_attributes:
-        return None
-    feature_name = extended_attributes['RuntimeEnabled']
+    feature_name = runtime_feature_name(definition_or_member)
+
+    # If an API experiment is on the method/attribute, it overrides the runtime
+    # enabled status. For now, we are unconditionally installing experimental
+    # attributes/methods, so we are acting as though the runtime enabled
+    # function doesn't exist. (It is checked in the generated
+    # ExperimentalFeatures function, instead)
+    experiment_name = api_experiment_name(definition_or_member)
+    if not feature_name or experiment_name:
+        return
     return 'RuntimeEnabledFeatures::%sEnabled' % uncapitalize(feature_name)