Fixing Heap::Available() to return total of all spaces.
Fixing Heap::Available() to return total of all spaces.

The Heap::Available method adds up the available size from only 4 of
the spaces. This CL fixes the method to return total of all spaces.

BUG=481504
LOG=N

Review URL: https://codereview.chromium.org/1141693003

Cr-Commit-Position: 972c6d2dc6dd5efdad1377c0d224e03eb8f276f7@{#28566}

UniversalFuture/moosh,UniversalFuture/moosh,UniversalFuture/moosh,UniversalFuture/moosh