V8 bindings gen: Error if FeaturePolicy and SecureContext together.

This check was previously added for OriginTrialEnabled and SecureContext
(r461653). This applies the same check to FeaturePolicy which has the
same limitation (i.e., this *should* work but currently generates broken
code where FeaturePolicy is totally ignored, and therefore must be a
compile-time error for now.

BUG=695123

Review-Url: https://codereview.chromium.org/2802873003
Cr-Commit-Position: refs/heads/master@{#462730}

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

@@ -423,6 +423,12 @@ def origin_trial_enabled_function_name(definition_or_member):
                         'not be specified on the same definition: %s'
                         % definition_or_member.name)
 
+    if is_feature_policy_enabled and 'SecureContext' in extended_attributes:
+        raise Exception('[FeaturePolicy] and [SecureContext] must '
+                        'not be specified on the same definition '
+                        '(see https://crbug.com/695123 for workaround): %s'
+                        % definition_or_member.name)
+
     if is_feature_policy_enabled:
         includes.add('bindings/core/v8/ScriptState.h')
         includes.add('platform/feature_policy/FeaturePolicy.h')