Reduce platform/heap/ wtf includes.

Rely on wtf/Forward.h where possible, reducing CPP's #include count
ever so slightly when processing platform/heap/Handle.h

R=
BUG=420515

Review URL: https://codereview.chromium.org/966243002

git-svn-id: svn://svn.chromium.org/blink/trunk@191082 bbb929c8-8fbe-4397-9dbb-9b2b20218538
4 files changed
tree: ba308e10b8405861168adf97600a6eb8503a4a59
  1. third_party/