Oilpan build fix after InspectorStyleSheet changes.

TBR=haraken@chromium.org
NOTRY=true

Review URL: https://codereview.chromium.org/225653002

git-svn-id: svn://svn.chromium.org/blink/trunk@170873 bbb929c8-8fbe-4397-9dbb-9b2b20218538
Oilpan: Clean up the way a precise GC is triggered at the end of the current event loop

- Currently collectGarbage() in js-test.js needs to run multiple event loops to collect all garbage. However, if we have a way to trigger multiple precise GCs at the end of the current event loop, we can just run only one event loop in collectGarbage() in js-test.js. This CL makes the change.

- Remove ThreadState::StackState from Heap::collectAllGarbage(), because the StackState must always be NoHeapPointersOnStack when Heap::collectAllGarbage() is called.

- Remove Heap::GCType. Rather than having the GCType flag, it is better to have Heap::setForcePreciseGCForTesting(). See the comment in ImageBitmapTest.cpp in the CL.

- Trigger multiple Heap::collectGarbage() in V8GCController::gcEpilogue(). See the comment in V8GCController::gcEpilogue() for more details.

Review URL: https://codereview.chromium.org/223303002

git-svn-id: svn://svn.chromium.org/blink/trunk@170874 bbb929c8-8fbe-4397-9dbb-9b2b20218538