Extends the functionality of Managed<T> to track an estimated size
for the external memory associated with an instance of Managed<T>
in order to allow for proper accounting in the garbage collector.

R=mstarzinger@chromium.org
CC=ulan@chromium.org

Cq-Include-Trybots: luci.v8.try:v8_linux_noi18n_rel_ng
Change-Id: I8c49c6245eaf267c9264ebb93b43d5dfbf4671fd
Reviewed-on: https://chromium-review.googlesource.com/1076332
Commit-Queue: Ben Titzer <titzer@chromium.org>
Reviewed-by: Michael Starzinger <mstarzinger@chromium.org>
Reviewed-by: Ulan Degenbaev <ulan@chromium.org>
Cr-Commit-Position: refs/heads/master@{#53433}

This CL simplifies and extends the implementation of Managed<T>
and now uses a std::shared_ptr<T> underneath in order to offer
cross-isolate management of C++ allocated memory.

R=mstarzinger@chromium.org
CC=ulan@chromium.org

Bug: v8:7424
Cq-Include-Trybots: luci.v8.try:v8_linux_noi18n_rel_ng
Change-Id: Id43a26f565677e8c9cdfd73810568d4f2b1871fe
Reviewed-on: https://chromium-review.googlesource.com/1028190Reviewed-by: Michael Starzinger <mstarzinger@chromium.org>
Commit-Queue: Ben Titzer <titzer@chromium.org>
Cr-Commit-Position: refs/heads/master@{#52820}

Test that Managed objects get collected if they are not referenced any
more.

R=ulan@chromium.org

Bug: v8:7628
Change-Id: I4a594ebe835071d76d7a6e2ddee6a6092b3e4a31
Reviewed-on: https://chromium-review.googlesource.com/999482Reviewed-by: Ulan Degenbaev <ulan@chromium.org>
Commit-Queue: Clemens Hammacher <clemensh@chromium.org>
Cr-Commit-Position: refs/heads/master@{#52438}

Rename Managed::New to Managed::From (since it takes ownership of an
existing object), and re-introduce Managed::Allocate, which allocates
a new object and stores it in a Managed.

R=titzer@chromium.org

Change-Id: I20b0750697fbe7d56d3816b19919c31e389278b3
Reviewed-on: https://chromium-review.googlesource.com/645806Reviewed-by: Ben Titzer <titzer@chromium.org>
Commit-Queue: Clemens Hammacher <clemensh@chromium.org>
Cr-Commit-Position: refs/heads/master@{#47794}

* Avoid "using namespace" statements, which trigger clang's -Wheader-hygiene
  warnings in jumbo builds.
* Undefine created macros at the end of source files.

BUG=chromium:746958

Change-Id: I5d25432c314437f607b0e1be22765a6764267ba6
Reviewed-on: https://chromium-review.googlesource.com/610962Reviewed-by: Jakob Kummerow <jkummerow@chromium.org>
Commit-Queue: Mostyn Bramley-Moore <mostynb@opera.com>
Cr-Commit-Position: refs/heads/master@{#47347}

For each Managed<T> (which is a Foreign), we create a weak global handle
with a finalizer which deletes the referenced C++ object once the
Foreign is dead.
Before calling this finalizer, the garbage collector needs to mark the
referenced object black (i.e. live), because the finalizer might
resurrect it.
Since this is never done for managed objects, we can use the more
lightweight phantom handle semantics, which allows the referenced
object to be garbage collected right away.

However, we can't access the global handle via the WeakCallbackInfo,
because the global handle will already be garbage collected. So we need
to store it explicitly. This is solved by storing the global handle
together with the finalizer.
In order to implement this, ownership of the ManagedObjectFinalizer
is moved from the isolate to the managed object.

R=ulan@chromium.org, mtrofin@chromium.org
BUG=v8:6505, chromium:734345

Change-Id: I94a245df601f70e19355d82439d30099e159231b
Reviewed-on: https://chromium-review.googlesource.com/539578
Commit-Queue: Clemens Hammacher <clemensh@chromium.org>
Reviewed-by: Ulan Degenbaev <ulan@chromium.org>
Cr-Commit-Position: refs/heads/master@{#46036}

Native resources allocated by v8, as internal implementation detail,
and held by a Foreign object, must be released when the Isolate is
torn down. Example: wasm::WasmModule allocated by wasm compile, and
held throughout the lifetime of the WebAssembly.Module object.

This change:
- Extends Managed<CppType> with a mechanism for doing just that
- Separates the role of Managed<CppType> to be strictly an owner of
the lifetime of the native resource. For cases where that's not
desirable, we can polymorphically use Foregin.
- moves managed.h out of wasm, since it's not wasm-specific.

BUG=680065

Review-Url: https://codereview.chromium.org/2676513008
Cr-Commit-Position: refs/heads/master@{#43350}