Revert 157005 "Ensure that Vector destruction always clears the ..."

> Ensure that Vector destruction always clears the buffer pointer.
> 
> This was previously the case, with the exception of inline-buffer Vectors in
> "inline storage" mode.
> 
> In the process, some code cleanups were performed:
> - Removed unused releaseBuffer().
> - Added a little LIKELY / UNLIKELY.
> - Removed a lot of redundant branches.
> - Less work and two removed branches from the destructor path.
> 
> Saves 100KB from a GCC-compiled Chrome binary. No real difference on clang,
> which seems to inline very differently.
> 
> BUG=270545
> R=abarth@chromium.org, tsepez@chromium.org
> 
> Review URL: https://codereview.chromium.org/23531010

TBR=cevans@chromium.org

Review URL: https://codereview.chromium.org/23858004

git-svn-id: svn://svn.chromium.org/blink/trunk@157267 bbb929c8-8fbe-4397-9dbb-9b2b20218538