This patch moves the following parsing methods to ParserBase:

- ParseScopedStatement
- ParseVariableStatement
- ParseDebuggerStatement
- ParseV8Intrinsic

It also cleans up the implementation-specific use counter mechanism.

R=adamk@chromium.org, marja@chromium.org
BUG=
LOG=N

Review-Url: https://codereview.chromium.org/2318263002
Cr-Commit-Position: refs/heads/master@{#39272}