Oilpan: move platform speech objects to the heap.

With the Speech API now using Oilpan by default, follow up and also
heap allocate the platform-level intermediary objects.

R=tkent@chromium.org,haraken@chromium.org
BUG=340522

Review URL: https://codereview.chromium.org/339823003

git-svn-id: svn://svn.chromium.org/blink/trunk@176321 bbb929c8-8fbe-4397-9dbb-9b2b20218538
Removed the redundant !this check (fix Clang's -Wundefined-bool-conversion warning)

BUG=381910
R=jochen@chromium.org

Review URL: https://codereview.chromium.org/339173002

git-svn-id: svn://svn.chromium.org/blink/trunk@176322 bbb929c8-8fbe-4397-9dbb-9b2b20218538