This enables adding more language modes in the future.

For maximum flexibility, LanguageMode is a bitmask, so we're not restricted to
use a sequence of language modes which are progressively stricter, but we can
express the language mode as combination of features.

For now, LanguageMode can only be "sloppy" or "strict", and there are
STATIC_ASSERTS in places which need to change when more modes are added.

LanguageMode is a bit like the old LanguageMode when "extended" mode was still
around (see https://codereview.chromium.org/8417035 and
https://codereview.chromium.org/181543002 ) except that it's transmitted through
all the layers (there's no StrictModeFlag).

BUG=

Review URL: https://codereview.chromium.org/894683003

Cr-Commit-Position: refs/heads/master@{#26419}

Both SameValue and SameValueZero consider different NaNs equal, so we
better assign the same hash value to all NaNs.

BUG=v8:3859
LOG=y
R=verwaest@chromium.org

Review URL: https://codereview.chromium.org/897593002

Cr-Commit-Position: refs/heads/master@{#26391}

BUG=454091
LOG=Y

Review URL: https://codereview.chromium.org/895573002

Cr-Commit-Position: refs/heads/master@{#26380}

BUG=chromium:437713, v8:3832
LOG=Y

Review URL: https://codereview.chromium.org/885003002

Cr-Commit-Position: refs/heads/master@{#26354}

R=svenpanne@chromium.org

Review URL: https://codereview.chromium.org/877753007

Cr-Commit-Position: refs/heads/master@{#26346}

This reverts commit 6a4c0a3b and commit
0deaa4b6 for breaking GCC bots.

TBR=svenpanne@chromium.org

Review URL: https://codereview.chromium.org/893533003

Cr-Commit-Position: refs/heads/master@{#26342}

R=svenpanne@chromium.org

Review URL: https://codereview.chromium.org/888613002

Cr-Commit-Position: refs/heads/master@{#26340}

BUG=chromium:448711
LOG=y

Review URL: https://codereview.chromium.org/861173004

Cr-Commit-Position: refs/heads/master@{#26289}

BUG=

Review URL: https://codereview.chromium.org/873233002

Cr-Commit-Position: refs/heads/master@{#26274}

BUG=

Review URL: https://codereview.chromium.org/873623002

Cr-Commit-Position: refs/heads/master@{#26242}

Use std::numeric_limits<double>::quiet_NaN() and
std::numeric_limits<float>::quiet_NaN() instead.

Review URL: https://codereview.chromium.org/864803002

Cr-Commit-Position: refs/heads/master@{#26195}

BUG=

Review URL: https://codereview.chromium.org/861773002

Cr-Commit-Position: refs/heads/master@{#26173}

Use RETURN_ON_EXCEPTION rather than .Assert when setting .length, which may fail due to stack overflow.

BUG=449447
LOG=n

Review URL: https://codereview.chromium.org/863693002

Cr-Commit-Position: refs/heads/master@{#26170}

This method circumvented JS semantics, and should not be used.

BUG=

Review URL: https://codereview.chromium.org/854493004

Cr-Commit-Position: refs/heads/master@{#26157}

PropertyKind:
  DATA -> kData
  ACCESSOR -> kAccessor

PropertyType:
  FIELD -> DATA
  CONSTANT -> DATA_CONSTANT
  ACCESSOR_FIELD -> ACCESSOR
  CALLBACKS -> ACCESSOR_CONSTANT

PropertyLocation:
  IN_OBJECT -> kField
  IN_DESCRIPTOR -> kDescriptor

StoreMode:
  FORCE_IN_OBJECT -> FORCE_FIELD

FieldDescriptor -> DataDescriptor
ConstantDescriptor -> DataConstantDescriptor
CallbacksDescriptor -> AccessorConstantDescriptor

Review URL: https://codereview.chromium.org/856503002

Cr-Commit-Position: refs/heads/master@{#26146}

R=yangguo@chromium.org

Review URL: https://codereview.chromium.org/804713006

Cr-Commit-Position: refs/heads/master@{#26145}

R=rossberg@chromium.org

Review URL: https://codereview.chromium.org/841213003

Cr-Commit-Position: refs/heads/master@{#26112}

BUG=

Review URL: https://codereview.chromium.org/845403002

Cr-Commit-Position: refs/heads/master@{#26044}

R=bmeurer@chromium.org
BUG=

Review URL: https://codereview.chromium.org/809333002

Cr-Commit-Position: refs/heads/master@{#26020}

Instead, just use DCHECKs. The builders that want them in release mode
should already be useding dcheck_always_on anyways

BUG=none
R=machenbach@chromium.org
LOG=y

Review URL: https://codereview.chromium.org/841083002

Cr-Commit-Position: refs/heads/master@{#26001}

Instead of using only \n as line terminator, we now use the definition
in http://www.ecma-international.org/ecma-262/5.1/#sec-7.3

R=marja@chromium.org
BUG=v8:2825
LOG=Y

Review URL: https://codereview.chromium.org/821383009

Cr-Commit-Position: refs/heads/master@{#25989}

R=jochen@chromium.org

BUG=

Review URL: https://codereview.chromium.org/834443004

Cr-Commit-Position: refs/heads/master@{#25981}

This is not needed anymore since all ICs use weak cells to embed maps.

BUG=v8:3629
LOG=N

Review URL: https://codereview.chromium.org/817223003

Cr-Commit-Position: refs/heads/master@{#25928}

This avoids touching the Array prototype, which may have been tampered with.

BUG=chromium:443982
LOG=n

Review URL: https://codereview.chromium.org/820503005

Cr-Commit-Position: refs/heads/master@{#25908}

BUG=v8:3629
LOG=N

Review URL: https://codereview.chromium.org/812353002

Cr-Commit-Position: refs/heads/master@{#25905}

BUG=chromium:442703
LOG=n
R=mvstanton@chromium.org

Review URL: https://codereview.chromium.org/809723002

Cr-Commit-Position: refs/heads/master@{#25844}

Review URL: https://codereview.chromium.org/805453002

Cr-Commit-Position: refs/heads/master@{#25842}

There are no users of this infrastructure yet, so it's behind an off-by-default flag.

Review URL: https://codereview.chromium.org/768633002

Cr-Commit-Position: refs/heads/master@{#25829}

Review URL: https://codereview.chromium.org/804993002

Cr-Commit-Position: refs/heads/master@{#25822}

Such properties never notified prior to r21558, but the combination of
that change and r23163 led to sending notifications when they were
set via Object.defineProperty (but not when set via other means).

This also allows some cleanup in v8natives.js and objects.cc,
both of which were doing unnecessary contortions to produce the right
change records.

BUG=v8:3745
LOG=n

Review URL: https://codereview.chromium.org/791243002

Cr-Commit-Position: refs/heads/master@{#25806}

FORCE_FIELD -> FORCE_IN_OBJECT,
ALLOW_AS_CONSTANT -> ALLOW_IN_DESCRIPTOR.

Review URL: https://codereview.chromium.org/799723003

Cr-Commit-Position: refs/heads/master@{#25803}

Review URL: https://codereview.chromium.org/801813002

Cr-Commit-Position: refs/heads/master@{#25802}

FINAL implies OVERRIDE, which in turn implies virtual, so there's no need to use
more than one of these. The Google C++ style guide even requires this, see
http://google-styleguide.googlecode.com/svn/trunk/cppguide.html#Inheritance.

While we're here, port r24662 to x87.

The net result is that v8 compiles again with a current clang.

BUG=v8:3753
LOG=y

Review URL: https://codereview.chromium.org/797943002

Cr-Commit-Position: refs/heads/master@{#25792}

This completes the first round of optimizations for Map and Set.
All non-key-dependent methods now have a Hydrogen version, and
for keyed methods, string versions are optimized.

Review URL: https://codereview.chromium.org/796503002

Cr-Commit-Position: refs/heads/master@{#25763}

They both now run fast (due to utilizing transitions instead of always
creating new maps) and sealed or non-extensible objects can stay in
fast mode after transitioning.

This almost entirely reuses the code for transitioning objects
frozen by Object.freeze(), with the added benefit of freeing
up a bit on the map (we no longer keep track of frozen-ness,
as that bit wasn't used for anything interesting).

BUG=v8:3662,chromium:115960
LOG=y

Review URL: https://codereview.chromium.org/776143005

Cr-Commit-Position: refs/heads/master@{#25759}

Reland of "TransitionArray now uses <is_data_property, name, attributes> tuple as a key, which allows to have several entries for the same property name."

Review URL: https://codereview.chromium.org/793453004

Cr-Commit-Position: refs/heads/master@{#25750}

When compiling with the macro DCHECK_ALWAYS_ON defined, DCHECKs and
supporting code gets compiled and enabled.

This increases test coverage for chromium release buildbots

BUG=v8:3731
R=jkummerow@chromium.org
LOG=y

Review URL: https://codereview.chromium.org/760213005

Cr-Commit-Position: refs/heads/master@{#25701}

This combines Map::DoneInobjectSlackTracking and Map::ConstructionCount into one more generic 4-bit counter.

Counter values from 15 down to 8 are used for in-object slack tracking, values from 7 down to 0 are free to be used for a new counter when in-object slack tracking is inactive.

Review URL: https://codereview.chromium.org/767253002

Cr-Commit-Position: refs/heads/master@{#25689}

This relands macroassembler instructions and weak cell caching and
does not include parts that caused "Linux ASan LSan" test failures.

BUG=v8:3663
LOG=N

Review URL: https://codereview.chromium.org/764003003

Cr-Commit-Position: refs/heads/master@{#25615}

Revert of Use weak cells in map checks in polymorphic ICs. (patchset #8 id:140001 of https://codereview.chromium.org/753993003/)

Reason for revert:
[Sheriff] Speculative revert for breaking chromium asan (roll blocker):
http://build.chromium.org/p/client.v8/builders/Linux%20ASan%20LSan%20Tests%20%281%29/builds/1683

Original issue's description:
> Use weak cells in map checks in polymorphic ICs.
>
> BUG=v8:3663
> LOG=N

TBR=mvstanton@chromium.org,akos.palfi@imgtec.com,weiliang.lin@intel.com,ulan@chromium.org
NOTREECHECKS=true
NOTRY=true
BUG=v8:3663

Review URL: https://codereview.chromium.org/771033003

Cr-Commit-Position: refs/heads/master@{#25597}