[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..ab36011c4b4ad102faab070c84aeaadf9d562af1 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(interface):

[haraken, 2015/12/30 00:25:32]

interface => definition_or_member ?

[Daniel Nishi, 2015/12/30 22:05:50]

Done.

+    return 'APIExperimentEnabled' in interface.extended_attributes
+
+
+def api_experiment_name(interface):
+    return interface.extended_attributes['APIExperimentEnabled'] if is_api_experiment_enabled(interface) 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:

[haraken, 2015/12/30 00:25:32]

Why do we need to check 'not feature_name'? Aren't we just ignoring the
[RuntimeEnabled] if [APIExperimentEnabled] is specified at the same time?

[Daniel Nishi, 2015/12/30 22:05:50]

https://codereview.chromium.org/1538663003/ uses the FeatureName to generate the
ExperimentalFeatures::%sEnabled function. Without a feature name, we don't know
what to use.

+        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 experiment is on the method/attribute, it overrides the runtime

[haraken, 2015/12/30 00:25:32]

experiment => API experiment

("experiment" sounds too generic.)

[Daniel Nishi, 2015/12/30 22:05:50]

Done.

+    # 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)