MIPS: Introduce intrinsics for double values in Javascript.

Port r19704 (120500a)

Patch from Balazs Kilvady <kilvadyb@homejinni.com>.

BUG=
R=plind44@gmail.com

Review URL: https://codereview.chromium.org/189913005

git-svn-id: https://v8.googlecode.com/svn/branches/bleeding_edge@19732 ce2b1a6d-e550-0410-aec6-3dcde31c8c00
MIPS: Consistenly handle power-of-2 divisors in division-like operations.

Port r19715 (0d6d244)

Original commit message:
Lithium currently supports 3 division-like operations on integral
operands: "Normal" division (rounding towards zero), flooring division
(rounding towards -Infinity) and modulus calculation (the counterpart
for the "normal" division). For divisors which are a power of 2, one can
efficiently use some bit fiddling to avoid the actual division for such
operations. This CL cleanly splits off these operations into separate
Lithium instructions, making the code much more maintainable and more
consistent across platforms.

There are 2 basic variations of these bit fiddling algorithms: One
involving branches and a seemingly more clever one without branches.
Choosing between the two is not as easy as it seems: Benchmarks (and
probably real-world) programs seem to favor positive dividends,
registers and shifting units are sometimes scarce resources, and branch
prediction is quite good in modern processors. Therefore only the
"normal" division by a power of 2 is implemented in a branch-free
manner, this seems to be the best approach in practice. If this turns
out to be wrong, we can easily and locally change this.

BUG=
R=plind44@gmail.com

Review URL: https://codereview.chromium.org/189433008

Patch from Balazs Kilvady <kilvadyb@homejinni.com>.

git-svn-id: https://v8.googlecode.com/svn/branches/bleeding_edge@19733 ce2b1a6d-e550-0410-aec6-3dcde31c8c00
Enable Object.observe by default

R=rossberg@chromium.org, rossberg
BUG=v8:2409
LOG=Y

Review URL: https://codereview.chromium.org/183683022

git-svn-id: https://v8.googlecode.com/svn/branches/bleeding_edge@19734 ce2b1a6d-e550-0410-aec6-3dcde31c8c00
Revert "Enable Object.observe by default"

TBR=rossberg
BUG=

Review URL: https://codereview.chromium.org/190853007

git-svn-id: https://v8.googlecode.com/svn/branches/bleeding_edge@19735 ce2b1a6d-e550-0410-aec6-3dcde31c8c00
Reland "Enable Object.observe by default"

Original Issue: https://codereview.chromium.org/183683022/

TBR=rossberg
BUG=v8:2409
LOG=Y

Review URL: https://codereview.chromium.org/189513010

git-svn-id: https://v8.googlecode.com/svn/branches/bleeding_edge@19736 ce2b1a6d-e550-0410-aec6-3dcde31c8c00
Merge remote-tracking branch 'upstream/master'