All function which potentially do heap allocations now take a Handle
on a WasmDebugInfo. This unfortunately requires to make some function
static, since otherwise the "this" pointer would not be handlified.

R=ahaas@chromium.org, titzer@chromium.org
BUG=chromium:613110

Review-Url: https://codereview.chromium.org/2074933005
Cr-Commit-Position: refs/heads/master@{#37099}