Make V8PrivateProperty::SymbolKey class is_trivially_constructible

A class which is not trivially constructible might bloat out code size.

The member variable |desc_| of class V8PrivateProperty::SymbolKey is used for just a description of a private property, so we can remove the variable.

This CL guarantees that V8PrivateProperty::SymbolKey is is_trivially_constructible.

Bug: 715418
Change-Id: I7f44e4e70430b66275b001c99974326556d38477
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1880778
Commit-Queue: Marina Sakai <marinasakai@google.com>
Reviewed-by: Yuki Shiino <yukishiino@chromium.org>
Reviewed-by: Hitoshi Yoshida <peria@chromium.org>
Cr-Commit-Position: refs/heads/master@{#710246}

third_party/blink/renderer/bindings/templates/attributes.cc.tmpl

@@ -41,8 +41,7 @@ const v8::FunctionCallbackInfo<v8::Value>& info
 
   {% if attribute.is_save_same_object %}
   // [SaveSameObject]
-  static const V8PrivateProperty::SymbolKey
-      save_same_object_key("{{cpp_class}}#{{attribute.camel_case_name}}");
+  static const V8PrivateProperty::SymbolKey save_same_object_key;
   auto private_same_object =
       V8PrivateProperty::GetSymbol(info.GetIsolate(), save_same_object_key);
   {
@@ -77,8 +76,7 @@ const v8::FunctionCallbackInfo<v8::Value>& info
       V8PrivateProperty::GetHistoryStateSymbol(info.GetIsolate());
   {% else %}
   {% if not attribute.private_property_is_shared_between_getter_and_setter %}
-  static const V8PrivateProperty::SymbolKey
-      {{attribute.private_property_key_name}}("{{cpp_class}}#{{attribute.camel_case_name}}");
+  static const V8PrivateProperty::SymbolKey {{attribute.private_property_key_name}};
 
   {% endif %}
   V8PrivateProperty::Symbol property_symbol =

third_party/blink/renderer/bindings/templates/interface_base.cc.tmpl

@@ -92,8 +92,7 @@ static void (*{{method.name}}MethodForPartialInterface)(const v8::FunctionCallba
 {% for world_suffix in attribute.world_suffixes %}
 {% if attribute.private_property_is_shared_between_getter_and_setter %}
 // Define a private property key shared between getter and setter.
-static const V8PrivateProperty::SymbolKey
-    {{attribute.private_property_key_name}}("{{cpp_class}}#{{attribute.camel_case_name}}");
+static const V8PrivateProperty::SymbolKey {{attribute.private_property_key_name}};
 {% endif %}
 
 {% if attribute.does_generate_getter %}

third_party/blink/renderer/bindings/tests/results/core/v8_test_object.cc

@@ -1993,8 +1993,7 @@ static void ActivityLoggingSetterForAllWorldsLongAttributeAttributeSetter(
 }
 
 // Define a private property key shared between getter and setter.
-static const V8PrivateProperty::SymbolKey
-    cached_attribute_any_attribute_key("TestObject#CachedAttributeAnyAttribute");
+static const V8PrivateProperty::SymbolKey cached_attribute_any_attribute_key;
 
 static void CachedAttributeAnyAttributeAttributeGetter(const v8::FunctionCallbackInfo<v8::Value>& info) {
   v8::Local<v8::Object> holder = info.Holder();
@@ -2046,8 +2045,7 @@ static void CachedAttributeAnyAttributeAttributeSetter(
 }
 
 // Define a private property key shared between getter and setter.
-static const V8PrivateProperty::SymbolKey
-    cached_array_attribute_key("TestObject#CachedArrayAttribute");
+static const V8PrivateProperty::SymbolKey cached_array_attribute_key;
 
 static void CachedArrayAttributeAttributeGetter(const v8::FunctionCallbackInfo<v8::Value>& info) {
   v8::Local<v8::Object> holder = info.Holder();
@@ -2108,8 +2106,7 @@ static void ReadonlyCachedAttributeAttributeGetter(const v8::FunctionCallbackInf
   TestObject* impl = V8TestObject::ToImpl(holder);
 
   // [CachedAttribute]
-  static const V8PrivateProperty::SymbolKey
-      readonly_cached_attribute_key("TestObject#ReadonlyCachedAttribute");
+  static const V8PrivateProperty::SymbolKey readonly_cached_attribute_key;
 
   V8PrivateProperty::Symbol property_symbol =
       V8PrivateProperty::GetSymbol(info.GetIsolate(),
@@ -2132,8 +2129,7 @@ static void ReadonlyCachedAttributeAttributeGetter(const v8::FunctionCallbackInf
 }
 
 // Define a private property key shared between getter and setter.
-static const V8PrivateProperty::SymbolKey
-    cached_string_or_none_attribute_key("TestObject#CachedStringOrNoneAttribute");
+static const V8PrivateProperty::SymbolKey cached_string_or_none_attribute_key;
 
 static void CachedStringOrNoneAttributeAttributeGetter(const v8::FunctionCallbackInfo<v8::Value>& info) {
   v8::Local<v8::Object> holder = info.Holder();
@@ -3145,8 +3141,7 @@ static void RaisesExceptionTestInterfaceEmptyAttributeAttributeSetter(
 }
 
 // Define a private property key shared between getter and setter.
-static const V8PrivateProperty::SymbolKey
-    cached_attribute_raises_exception_getter_any_attribute_key("TestObject#CachedAttributeRaisesExceptionGetterAnyAttribute");
+static const V8PrivateProperty::SymbolKey cached_attribute_raises_exception_getter_any_attribute_key;
 
 static void CachedAttributeRaisesExceptionGetterAnyAttributeAttributeGetter(const v8::FunctionCallbackInfo<v8::Value>& info) {
   v8::Local<v8::Object> holder = info.Holder();
@@ -4125,8 +4120,7 @@ static void SaveSameObjectAttributeAttributeGetter(const v8::FunctionCallbackInf
   v8::Local<v8::Object> holder = info.Holder();
 
   // [SaveSameObject]
-  static const V8PrivateProperty::SymbolKey
-      save_same_object_key("TestObject#SaveSameObjectAttribute");
+  static const V8PrivateProperty::SymbolKey save_same_object_key;
   auto private_same_object =
       V8PrivateProperty::GetSymbol(info.GetIsolate(), save_same_object_key);
   {
@@ -4161,8 +4155,7 @@ static void StaticSaveSameObjectAttributeAttributeGetter(const v8::FunctionCallb
   v8::Local<v8::Object> holder = info.Holder();
 
   // [SaveSameObject]
-  static const V8PrivateProperty::SymbolKey
-      save_same_object_key("TestObject#StaticSaveSameObjectAttribute");
+  static const V8PrivateProperty::SymbolKey save_same_object_key;
   auto private_same_object =
       V8PrivateProperty::GetSymbol(info.GetIsolate(), save_same_object_key);
   {

third_party/blink/renderer/platform/bindings/v8_private_property.cc

@@ -11,6 +11,18 @@
 
 namespace blink {
 
+// As SymbolKey is widely used, numerous instances of SymbolKey are created,
+// plus all the instances have static storage duration (defined as static
+// variables).  Thus, it's important to make SymbolKey
+// trivially-constructible/destructible so that compilers can remove all the
+// constructor/destructor calls and reduce the code size.
+static_assert(
+    std::is_trivially_constructible<V8PrivateProperty::SymbolKey>::value,
+    "SymbolKey is not trivially constructible");
+static_assert(
+    std::is_trivially_destructible<V8PrivateProperty::SymbolKey>::value,
+    "SymbolKey is not trivially destructible");
+
 v8::MaybeLocal<v8::Value> V8PrivateProperty::Symbol::GetFromMainWorld(
     ScriptWrappable* script_wrappable) {
   v8::Local<v8::Object> wrapper = script_wrappable->MainWorldWrapper(isolate_);
@@ -27,7 +39,7 @@ V8PrivateProperty::Symbol V8PrivateProperty::GetSymbol(
   auto iter = symbol_map.find(&key);
   v8::Local<v8::Private> v8_private;
   if (UNLIKELY(iter == symbol_map.end())) {
-    v8_private = CreateV8Private(isolate, key.GetDescription());
+    v8_private = CreateV8Private(isolate, nullptr);
     symbol_map.insert(&key, v8::Eternal<v8::Private>(isolate, v8_private));
   } else {
     v8_private = iter->value.Get(isolate);

third_party/blink/renderer/platform/bindings/v8_private_property.h

@@ -54,17 +54,16 @@ class ScriptWrappable;
 
 // Provides access to V8's private properties.
 //
-// Usage 1) Fast path to use a pre-registered symbol.
+// Usage 1) Path to use a pre-registered symbol.
 //   auto private_property = V8PrivateProperty::GetDOMExceptionError(isolate);
 //   v8::Local<v8::Object> object = ...;
 //   v8::Local<v8::Value> value;
 //   if (!private_property.GetOrUndefined(object).ToLocal(&value)) return;
 //   value = ...;
-//   private_property.set(object, value);
+//   private_property.Set(object, value);
 //
-// Usage 2) Slow path to create a global private symbol.
-//   /* |desc| is a description of the private property. */
-//   static const SymbolKey key(desc);
+// Usage 2) Access with a symbol key.
+//   static const SymbolKey key;
 //   auto private_property = V8PrivateProperty::GetSymbol(isolate, key);
 //   ...
 class PLATFORM_EXPORT V8PrivateProperty {
@@ -134,29 +133,21 @@ class PLATFORM_EXPORT V8PrivateProperty {
   // This class is used for a key to get Symbol.
   //
   // We can improve ability of tracking private properties by using an instance
-  // of this class. |desc_| is a description of the private property.
+  // of this class.
   class PLATFORM_EXPORT SymbolKey final {
    public:
-    // Note that, unlike a string class, the lifetime of |desc| must be longer
-    // than this SymbolKey, i.e. this SymbolKey does not copy |desc| nor have
-    // |desc| alive enough long.
-    explicit SymbolKey(const char* desc) : desc_(desc) {}
-
-    const char* GetDescription() const { return desc_; }
+    SymbolKey() = default;
 
    private:
     SymbolKey(const SymbolKey&) = delete;
     SymbolKey& operator=(const SymbolKey&) = delete;
-
-    const char* const desc_;
   };
 
 #define V8_PRIVATE_PROPERTY_DEFINE_GETTER(InterfaceName, KeyName)        \
   static Symbol V8_PRIVATE_PROPERTY_GETTER_NAME(/* // NOLINT */          \
                                                 InterfaceName, KeyName)( \
       v8::Isolate * isolate) {                                           \
-    static const SymbolKey private_property_key(                         \
-        V8_PRIVATE_PROPERTY_SYMBOL_STRING(InterfaceName, KeyName));      \
+    static const SymbolKey private_property_key;                         \
     return GetSymbol(isolate, private_property_key);                     \
   }
 
@@ -195,7 +186,7 @@ class PLATFORM_EXPORT V8PrivateProperty {
   // This is a hack for PopStateEvent to get the same private property of
   // History, named State.
   static Symbol GetHistoryStateSymbol(v8::Isolate* isolate) {
-    static const SymbolKey private_property_key("History#State");
+    static const SymbolKey private_property_key;
     return GetSymbol(isolate, private_property_key);
   }