Various places assume that GetExpression returns the locals for a frame.
Modify InterpretedFrames such that GetExpression(0) returns the first
local, not the fixed parts of the interpreter frame.

BUG=v8:4690,v8:4680
LOG=N

Review URL: https://codereview.chromium.org/1697223003

Cr-Commit-Position: refs/heads/master@{#34040}