This patch moves the following parsing method to ParserBase:

- ParseClassDeclaration
- ParseClassLiteral
- ParseNativeDeclaration

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

Committed: https://crrev.com/7818355363b7a66ff7709e33c72bfdef5eb21450
Review-Url: https://codereview.chromium.org/2368083002
Cr-Original-Commit-Position: refs/heads/master@{#39814}
Cr-Commit-Position: refs/heads/master@{#39829}