Previous changes with subclassable builtins and @@species were a bit
aggressive in making TypedArray.prototype.subarray act like the
ES2016 specification in terms of returning an instance of the
subclass as a result. It turns out that Node.js, and extracted
libraries for the web, subclass TypedArrays but don't expect the
subclass constructor to be called by subarray. @@species will provide
an escape hatch, but it has not shipped yet, and will take some time
for uptake by libraries.
For now, this patch makes TypedArray.prototype.subarray fall back to
constructing an instance of the parent TypedArray class, such as
Uint8Array.
R=adamk
LOG=Y
BUG=v8:4665
Review URL: https://codereview.chromium.org/1583773005
Cr-Commit-Position: refs/heads/master@{#33312}
This patch improves ArrayBuffer and TypedArray subclassing by adding
support for @@species and constructing outputs to certain methods
by creating an instance of the constructor determined by the
SpeciesConstructor algorithm, rather than fixed to a superclass or
naively the constructor. The new behavior is enabled by the
--harmony-species flag. Care is taken to not significantly change the
observable behavior when the flag is off. Previously, TypedArrays
already supported subclassing by reading the constructor of the
receiver, but ArrayBuffers did not, and this old behavior is
preserved and tested for, to avoid a multi-stage upgrade path and keep
things simple for users.
R=adamk
BUG=v8:4093
LOG=Y
Review URL: https://codereview.chromium.org/1574903004
Cr-Commit-Position: refs/heads/master@{#33223}
