Generally, methods that take a *TextBuffer pointer do not care how the
internal buffer is allocated, and so they could be used for either if
both were subclasses of a base class that contained the printing
methods. This CL makes that base class, and now TextBuffer and
ZoneTextBuffer now share the exact same set of methods for printing to
the internal buffer.
Since the base class is in platform, this does mean dropping the
overload of AddString for Dart String objects that was part of
ZoneTextBuffer. Instead, this CL just adds an intermediate call to
ToCString() for the small number of callers that used the overload,
keeping the printing interface the same for both.
In addition, one use of TextBuffer that then re-allocated the buffer
contents into the zone manually has been replaced with a ZoneTextBuffer
instead.
Change-Id: I438a085e7e20d55d93987fd7f36afd636f95955f
Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/157741
Reviewed-by: Ryan Macnak <rmacnak@google.com>
Commit-Queue: Tess Strickland <sstrickl@google.com>