[cleanup] Fix use of deprecated GetFunction method

Use MaybeLocal version of GetFunction in GinJavaBridgeObject as original
function is deprecated. Since the original code seems to react to other
failures by returning an empty Local<>, I've used the same pattern
rather than ToLocalChecked.

Bug: v8:7295, v8:8238
Change-Id: I634b4d7ec51c4874f9628f05fbf5106f10c0990c
Reviewed-on: https://chromium-review.googlesource.com/c/1348045Reviewed-by: Avi Drissman <avi@chromium.org>
Commit-Queue: Dan Elphick <delphick@chromium.org>
Cr-Commit-Position: refs/heads/master@{#610868}

content/renderer/java/gin_java_bridge_object.cc

@@ -89,10 +89,13 @@ v8::Local<v8::Value> GinJavaBridgeObject::GetNamedProperty(
     }
     known_methods_[property] = dispatcher_->HasJavaMethod(object_id_, property);
   }
-  if (known_methods_[property])
-    return GetFunctionTemplate(isolate, property)->GetFunction();
-  else
+  if (known_methods_[property]) {
+    return GetFunctionTemplate(isolate, property)
+        ->GetFunction(isolate->GetCurrentContext())
+        .FromMaybe(v8::Local<v8::Value>());
+  } else {
     return v8::Local<v8::Value>();
+  }
 }
 
 std::vector<std::string> GinJavaBridgeObject::EnumerateNamedProperties(