Assert to protect against polymorphic string loads fires on valid stores.

BUG=435477
LOG=N
R=jarin@chromium.org

Review URL: https://codereview.chromium.org/751513002

Cr-Commit-Position: refs/heads/master@{#25456}
Correctly escape RegExp source.

R=ulan@chromium.org
BUG=v8:3229
LOG=N

Review URL: https://codereview.chromium.org/736003002

Cr-Commit-Position: refs/heads/master@{#25457}
Fix mozilla expectations after regexp change.

TBR=ulan@chromium.org

Review URL: https://codereview.chromium.org/749963002

Cr-Commit-Position: refs/heads/master@{#25458}
Remove deprecated ShouldSelfOptimize machinery.

R=titzer@chromium.org

Review URL: https://codereview.chromium.org/582683002

Cr-Commit-Position: refs/heads/master@{#25459}
ARM64: skip flaky mozilla/ecma/Date/15.9.5.26-1 until it is fixed.

BUG=v8:3716
LOG=N

Review URL: https://codereview.chromium.org/746983002

Cr-Commit-Position: refs/heads/master@{#25460}
[turbofan] put spill slot reuse behind a flag

BUG=

Review URL: https://codereview.chromium.org/748773002

Cr-Commit-Position: refs/heads/master@{#25461}
Introduce a flag to change the new space growth factor

A useful value would be 4, so we get 1, 4, 16MB (instead of the default
value 2 which leads to 1, 2, 4, 8, 16)

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

Review URL: https://codereview.chromium.org/753513002

Cr-Commit-Position: refs/heads/master@{#25462}