[turbofan] add initial move optimizer

R=bmeurer@chromium.org

BUG=

Review URL: https://codereview.chromium.org/750813004

Cr-Commit-Position: refs/heads/master@{#25533}
Ensure double alignment when deserializing.

R=rmcilroy@chromium.org
BUG=chromium:436510
LOG=N
TEST=compile with V8_OOL_CONSTANT_POOL=1, run d8 with --verify-heap --test

Review URL: https://codereview.chromium.org/759823006

Cr-Commit-Position: refs/heads/master@{#25534}
Fast-to-slow migration should wipe out in-object space if it exists in the object after migration.

BUG=chromium:436816
LOG=N

Review URL: https://codereview.chromium.org/765473004

Cr-Commit-Position: refs/heads/master@{#25535}
Ship harmony-strings

R=rossberg@chromium.org, yangguo@chromium.org
LOG=Y

Review URL: https://codereview.chromium.org/761913002

Cr-Commit-Position: refs/heads/master@{#25536}
Add interceptor support for symbols

a revival of https://codereview.chromium.org/467013003

R=rossberg@chromium.org

BUG=

Review URL: https://codereview.chromium.org/760883002

Cr-Commit-Position: refs/heads/master@{#25537}
Add support for downloading clang

Still requires changes to gyp files to select the built-in clang as
compiler and make clang the default on the platforms we want it.

BUG=
R=dcarney@chromium.org,machenbach@chromium.org
LOG=n

Review URL: https://codereview.chromium.org/745963005

Cr-Commit-Position: refs/heads/master@{#25538}
Just print interesting idle notification events in --trace-idle-notification.

BUG=

Review URL: https://codereview.chromium.org/763063002

Cr-Commit-Position: refs/heads/master@{#25539}
Introduce a new growth criterion for the new space behind a flag

With this flag, we grow if more than 10% survived the last scavenge.

BUG=none
R=hpayer@chromium.org
LOG=n

Review URL: https://codereview.chromium.org/753543002

Cr-Commit-Position: refs/heads/master@{#25540}
MIPS: harmony-scoping: make assignment to 'const' a late error.

Port 6ac4de87a8b01500b066a3e401e921d2d84b42db

Original commit message:
Per TC39 Nov 2014 decision.

This patch also changes behavior for "legacy const": assignments to sloppy const in strict mode is now also a type error. This fixes v8:2243 and also brings us in compliance with other engines re assignment to function names (see updated webkit test), but might have bigger implications.
That change can easily be reverted by changing Variable::IsSignallingAssignmentToConst.

BUG=v8:3713,v8:2243
LOG=N

Review URL: https://codereview.chromium.org/766703002

Cr-Commit-Position: refs/heads/master@{#25541}
Switch backedge table in scheduler to use ZoneVector.

R=jarin@chromium.org

Review URL: https://codereview.chromium.org/761733002

Cr-Commit-Position: refs/heads/master@{#25542}
Start immediate dominator propagation at entry to floating control.

R=titzer@chromium.org

Review URL: https://codereview.chromium.org/761673004

Cr-Commit-Position: refs/heads/master@{#25543}
Just finalize incremental marking when marking is done in idle notification.

BUG=

Review URL: https://codereview.chromium.org/733893003

Cr-Commit-Position: refs/heads/master@{#25544}
Re-land: Distinguish beween final incremental mark-compact and full mark-compact event in IdleNotification.

BUG=
R=ulan@chromium.org

Review URL: https://codereview.chromium.org/765743002

Cr-Commit-Position: refs/heads/master@{#25545}
Just account for context disposal garbage collections in context disposal stats counters.

BUG=

Review URL: https://codereview.chromium.org/765773002

Cr-Commit-Position: refs/heads/master@{#25546}
Fix reduction result for branches in generic lowering.

R=bmeurer@chromium.org

Review URL: https://codereview.chromium.org/750333003

Cr-Commit-Position: refs/heads/master@{#25547}
Remove deprecated constant helpers from JSGenericLowering.

R=bmeurer@chromium.org

Review URL: https://codereview.chromium.org/761143002

Cr-Commit-Position: refs/heads/master@{#25548}