Remove unused old API GetSymbol() in V8PrivateProperty

In the previous CLs, we replaced all the old GetSymbol(), which uses void* as a key, with the new GetSybmol(), which uses an instance of SymbolKey.
So, this CL removes the unused old GetSymbol().

Bug: 715418
Change-Id: I465370f55ed07632c6f4d00804733c3c49aaab43
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1888858Reviewed-by: Hitoshi Yoshida <peria@chromium.org>
Reviewed-by: Kentaro Hara <haraken@chromium.org>
Reviewed-by: Yuki Shiino <yukishiino@chromium.org>
Commit-Queue: Marina Sakai <marinasakai@google.com>
Cr-Commit-Position: refs/heads/master@{#710673}

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

@@ -190,25 +190,6 @@ class PLATFORM_EXPORT V8PrivateProperty {
     return GetSymbol(isolate, private_property_key);
   }
 
-  // Returns a Symbol to access a private property. Symbol instances from same
-  // |key|s are guaranteed to access the same property. |desc| is a description
-  // of the property. By defining the key as the address of a static variable,
-  // the key is unique for each private property.
-  static Symbol GetSymbol(v8::Isolate* isolate, void* key, const char* desc) {
-    V8PrivateProperty* private_prop =
-        V8PerIsolateData::From(isolate)->PrivateProperty();
-    auto& symbol_map = private_prop->symbol_map_;
-    auto iter = symbol_map.find(key);
-    v8::Local<v8::Private> v8_private;
-    if (UNLIKELY(iter == symbol_map.end())) {
-      v8_private = CreateV8Private(isolate, desc);
-      symbol_map.insert(key, v8::Eternal<v8::Private>(isolate, v8_private));
-    } else {
-      v8_private = iter->value.Get(isolate);
-    }
-    return Symbol(isolate, v8_private);
-  }
-
   // Returns a Symbol to access a private property. Symbol instances from same
   // |key| are guaranteed to access the same property.
   static Symbol GetSymbol(v8::Isolate* isolate, const SymbolKey& key);