[Tracing] Add lookup support to AllocationRegister

[Tracing] Add lookup support to AllocationRegister

This adds a |Get| method to |AllocationRegister| which can be used to
change the context and size of an allocation after it has been inserted.
One possible use case of this is to post-annotate allocations with type
information, when this information is not available to the allocator,
but it is later in the program.

Because |AllocationRegister::Allocation| is now exposed mutably, its
|address| member has been made const. The hash of the address has to
match the bucket in which the |Allocation| is stored, so after insertion
the address must not be changed. This is enforced by making the member
const, at the cost of a few const violations in the implementation of
|AllocationRegister|.

BUG=574756
Committed: https://crrev.com/f57f47aa398e6ccd03b1888a176fe59e8a5cdea2
Cr-Commit-Position: refs/heads/master@{#368583}

[Ruud van Asseldonk, 2016-01-08 16:53:36]

ruuda@google.com changed reviewers:
+ primiano@chromium.org

[Ruud van Asseldonk, 2016-01-08 16:53:36]

Primiano, please take a look at this CL that adds support for post-annotating
allocations in the heap profiler.

Please read the commit message before reviewing for rationale.

[Primiano Tucci (use gerrit), 2016-01-11 11:08:54]

LGTM

[Ruud van Asseldonk, 2016-01-11 12:07:47]

On 2016/01/11 11:08:54, Primiano Tucci wrote:
> LGTM

Thanks. Before I land this, do you want me to add |const Allocation* Get(void*
address) const|? It would be 7 extra lines, with implementation identical to the
current |Get|.

[Primiano Tucci (use gerrit), 2016-01-11 13:03:35]

On 2016/01/11 12:07:47, Ruud van Asseldonk wrote:
> On 2016/01/11 11:08:54, Primiano Tucci wrote:
> > LGTM
> 
> Thanks. Before I land this, do you want me to add |const Allocation* Get(void*
> address) const|? It would be 7 extra lines, with implementation identical to
the
> current |Get|.

We can add a pure const getter if we'll need it, let's not over-code if there is
no use case right now.

[Ruud van Asseldonk, 2016-01-11 13:30:33]

The CQ bit was checked by ruuda@google.com

[commit-bot: I haz the power, 2016-01-11 13:30:41]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/1574493002/1
View timeline at
 https://chromium-cq-status.appspot.com/patch-timeline/1574493002/1

[commit-bot: I haz the power, 2016-01-11 14:49:12]

Committed patchset #1 (id:1)

[commit-bot: I haz the power, 2016-01-11 14:50:42]

Description was changed from

==========
[Tracing] Add lookup support to AllocationRegister

This adds a |Get| method to |AllocationRegister| which can be used to
change the context and size of an allocation after it has been inserted.
One possible use case of this is to post-annotate allocations with type
information, when this information is not available to the allocator,
but it is later in the program.

Because |AllocationRegister::Allocation| is now exposed mutably, its
|address| member has been made const. The hash of the address has to
match the bucket in which the |Allocation| is stored, so after insertion
the address must not be changed. This is enforced by making the member
const, at the cost of a few const violations in the implementation of
|AllocationRegister|.

BUG=574756
==========

to

==========
[Tracing] Add lookup support to AllocationRegister

This adds a |Get| method to |AllocationRegister| which can be used to
change the context and size of an allocation after it has been inserted.
One possible use case of this is to post-annotate allocations with type
information, when this information is not available to the allocator,
but it is later in the program.

Because |AllocationRegister::Allocation| is now exposed mutably, its
|address| member has been made const. The hash of the address has to
match the bucket in which the |Allocation| is stored, so after insertion
the address must not be changed. This is enforced by making the member
const, at the cost of a few const violations in the implementation of
|AllocationRegister|.

BUG=574756

Committed: https://crrev.com/f57f47aa398e6ccd03b1888a176fe59e8a5cdea2
Cr-Commit-Position: refs/heads/master@{#368583}
==========

[commit-bot: I haz the power, 2016-01-11 14:50:42]

Patchset 1 (id:??) landed as
https://crrev.com/f57f47aa398e6ccd03b1888a176fe59e8a5cdea2
Cr-Commit-Position: refs/heads/master@{#368583}