Fix nested Scoped*ForTest when the inner is implied by the outer

Previously, if feature A implies B, suppose both are disabled by
default, in the following situation:
  ScopedAForTest a;
  ScopedBForTest b;
feature B will be left enabled after the scope.

Now let Scoped*ForTest use the data field of the feature instead of
calling *Enabled() and Set*Enabled() (which are asymmetric when the
feature is implied).

RuntimeEnabledFeature backup and restore had the similar issue. Also
let them use data field instead of calling the methods.

Bug: 1061443
Change-Id: I28bfee510bf3e4491c11887d7f8c992d433b9702
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2103317Reviewed-by: Morten Stenshorne <mstensho@chromium.org>
Commit-Queue: Xianzhu Wang <wangxianzhu@chromium.org>
Cr-Commit-Position: refs/heads/master@{#750430}

third_party/blink/renderer/build/scripts/make_runtime_features.py

@@ -185,7 +185,8 @@ class RuntimeFeatureTestHelpersWriter(BaseRuntimeFeatureWriter):
 
     def _template_inputs(self):
         return {
-            'features': self._features,
+            # The test helpers don't support custom features.
+            'features': self._standard_features,
             'input_files': self._input_files,
             'header_guard': self._header_guard,
         }

third_party/blink/renderer/build/scripts/templates/runtime_enabled_features.cc.tmpl

@@ -14,18 +14,14 @@ namespace blink {
 
 RuntimeEnabledFeatures::Backup::Backup()
   : {% for feature in standard_features -%}
-{% if feature.in_origin_trial %}
-    {{feature.name.to_class_data_member()}}(RuntimeEnabledFeatures::{{feature.name}}EnabledByRuntimeFlag())
-{% else %}
-    {{feature.name.to_class_data_member()}}(RuntimeEnabledFeatures::{{feature.name}}Enabled())
-{% endif %}
+    {{feature.data_member_name}}(RuntimeEnabledFeatures::{{feature.data_member_name}})
     {%- if not loop.last %},
     {%+ endif -%}
     {% endfor %} {}
 
 void RuntimeEnabledFeatures::Backup::Restore() {
   {% for feature in standard_features %}
-  RuntimeEnabledFeatures::Set{{feature.name}}Enabled({{feature.name.to_class_data_member()}});
+  RuntimeEnabledFeatures::{{feature.data_member_name}} = {{feature.data_member_name}};
   {% endfor %}
 }
 

third_party/blink/renderer/build/scripts/templates/runtime_enabled_features.h.tmpl

@@ -49,7 +49,7 @@ class PLATFORM_EXPORT RuntimeEnabledFeatures {
 
    private:
     {% for feature in standard_features %}
-    bool {{feature.name.to_class_data_member()}};
+    bool {{feature.data_member_name}};
     {% endfor %}
   };
 
@@ -95,6 +95,8 @@ class PLATFORM_EXPORT RuntimeEnabledFeatures {
   {% endfor %}
 
  private:
+  friend class RuntimeEnabledFeaturesTestHelpers;
+
   {% for feature in standard_features %}
   static bool {{feature.data_member_name}};
   {% endfor %}

third_party/blink/renderer/build/scripts/templates/runtime_enabled_features_test_helpers.h.tmpl

@@ -11,33 +11,32 @@
 
 namespace blink {
 
-template <bool (&getter)(), void (&setter)(bool)>
-class ScopedRuntimeEnabledFeatureForTest {
+// Don't use this class directly. Use Scoped*ForTest instead.
+class RuntimeEnabledFeaturesTestHelpers {
  public:
-  ScopedRuntimeEnabledFeatureForTest(bool enabled)
-      : enabled_(enabled), original_(getter()) {
-    setter(enabled);
-  }
-
-  ~ScopedRuntimeEnabledFeatureForTest() {
-    CHECK_EQ(enabled_, getter());
-    setter(original_);
-  }
-
- private:
-  bool enabled_;
-  bool original_;
+  template <bool& data_member>
+  class ScopedRuntimeEnabledFeature {
+   public:
+    ScopedRuntimeEnabledFeature(bool enabled)
+        : enabled_(enabled), original_(data_member) { data_member = enabled; }
+    ~ScopedRuntimeEnabledFeature() {
+      CHECK_EQ(enabled_, data_member);
+      data_member = original_;
+    }
+   private:
+    bool enabled_;
+    bool original_;
+  };
+
+  {% for feature in features %}
+  using Scoped{{feature.name}} = ScopedRuntimeEnabledFeature<
+      RuntimeEnabledFeatures::{{feature.data_member_name}}>;
+  {% endfor %}
 };
 
 {% for feature in features %}
-typedef ScopedRuntimeEnabledFeatureForTest<
-{% if feature.in_origin_trial %}
-    RuntimeEnabledFeatures::{{feature.name}}EnabledByRuntimeFlag,
-{% else %}
-    RuntimeEnabledFeatures::{{feature.name}}Enabled,
-{% endif %}
-    RuntimeEnabledFeatures::Set{{feature.name}}Enabled>
-    Scoped{{feature.name}}ForTest;
+using Scoped{{feature.name}}ForTest =
+    RuntimeEnabledFeaturesTestHelpers::Scoped{{feature.name}};
 {% endfor %}
 }  // namespace blink