With this patch, every node in turbo-*.json has an opcode, a title, and
a label. The label field is new; the opcode and title were already
there. The title is for the mouseover text. The label is what will be
displayed in the graph view, unless it's too long, in which case only
the opcode will be displayed. (This is similar to the preexisting
behaviour of putting titles in labels, except that the titles were
rarely short enough to fit in a label.)

With this patch, the labels generated are in practice the same as the
titles we had before, except for LoadField and StoreField, which will be
rendered as LoadField[[+432]] and StoreField[[+432]] (if 432 was the
offset).

This diff adds an overloadable method

    virtual void Operator1<T>::PrintParameter(ostream&, PrintVerbosity)

for each type T to Operator1. Its default implementation just uses
operator<<(ostream&, T const&) and adds square brackets around it, but
it is overridden for FieldAccess to print "[+432]" in the example case.

BUG=
R=jarin,danno

Review-Url: https://codereview.chromium.org/2093013002
Cr-Commit-Position: refs/heads/master@{#37795}