Document Error class in dart:core

[kevmoo]

See this discussion: https://groups.google.com/a/dartlang.org/d/topic/misc/lx9CXiV3o30/discussion

At the moment, the Error class has no documentation.

Error docs should highlight the differences with the Exception class and when to use which.

See closed issue https://code.google.com/p/dart/issues/detail?id=9377

[lrhn]

Added Started label.

[lrhn]

Added Fixed label.

[DartBot]

This comment was originally written by [email protected]

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I also think that when its time to make available something like the "Java Pet Store",we should have real world implementations of both exceptions and Error Classes,since it seems that not everybody knows how to tell them apart.

[kevmoo]

See r31954