JSObject is slow: creating strings for keys and storing values by these keys after takes significant amount of time.
With this CL console methods (most of them collect top stack frame to calculate source location) are ~33% faster.
V8Debugger::captureStackTrace is ~50% faster.

BUG=v8:6189
R=yangguo@chromium.org
TBR=bmeurer@chromium.org

Review-Url: https://codereview.chromium.org/2789073002
Cr-Commit-Position: refs/heads/master@{#44344}