Currently to obtain a v8::Array out of a C array or a std::vector,
one needs to loop through the elements and call array->Set() multiple
times, and these calls go into v8::Object::Set() which can be slow.
This patch adds a new Array::New overload that converts a
Local<Value>* with known size into a Local<Array>.

Change-Id: I0a768f0e18eec51e78d58be455482ec6425ca188
Reviewed-on: https://chromium-review.googlesource.com/c/1317049Reviewed-by: Yang Guo <yangguo@chromium.org>
Reviewed-by: Adam Klein <adamk@chromium.org>
Commit-Queue: Joyee Cheung <joyee@igalia.com>
Cr-Commit-Position: refs/heads/master@{#57261}