Skip unnecessary v8::TryCatch in V8StringResource::prepare()

Since we're only interested in detecting and propagating an exception,
check whether v8::Value::ToString()'s return value is an empty handle
instead of using a v8::TryCatch local.

This is faster, since initializing a v8::TryCatch has non-zero cost, and
should also be less binary code (v8::Handle::IsEmpty() is inlined and
simply a null check.)

BUG=413257

Review URL: https://codereview.chromium.org/576323004

git-svn-id: svn://svn.chromium.org/blink/trunk@182476 bbb929c8-8fbe-4397-9dbb-9b2b20218538
Oilpan: make Supplementable tracing more regular.

With PersistentHeapSupplementable retired, follow up and only provide a
trace() method for a Supplementable that's on the heap.

No changes made for Supplements: an empty trace() method is still
provided for off-heap supplements, as this is the better solution
while we still are using the transition type WillBeHeapSupplement
for all the supplement objects.

R=haraken,zerny,wibling
BUG=395036

Review URL: https://codereview.chromium.org/587393002

git-svn-id: svn://svn.chromium.org/blink/trunk@182477 bbb929c8-8fbe-4397-9dbb-9b2b20218538
Mark media/gc-while-playing.html as not flaky

It is no longer failing after r182442:
https://codereview.chromium.org/587373002/

BUG=400659
NOTRY=true

Review URL: https://codereview.chromium.org/593013002

git-svn-id: svn://svn.chromium.org/blink/trunk@182478 bbb929c8-8fbe-4397-9dbb-9b2b20218538
DevTools: Fix compilation of the new "promises" module

TBR=aandrey
NOTRY=true

Review URL: https://codereview.chromium.org/589403002

git-svn-id: svn://svn.chromium.org/blink/trunk@182479 bbb929c8-8fbe-4397-9dbb-9b2b20218538
Oilpan: blink_heap_unittests: MapWithCustomWeaknessHandling and MapWithCustomWeaknessHandling have some leaks

1. we need a collectAllGarbage() at the end of test to do some clearing work.

R=ager@chromium.org, oilpan-reviews@chromium.org
BUG=416765

Review URL: https://codereview.chromium.org/589343002

git-svn-id: svn://svn.chromium.org/blink/trunk@182480 bbb929c8-8fbe-4397-9dbb-9b2b20218538