Allow patch files to add top-level declarations to the patched library.

Allow patch files to add top-level declarations to the patched library.

The patch library is loaded normally, and then non-patch methods and classes
are cloned and added to the patched library. To support methods from other
compilation units, all elements now has a scriptOverride field that lets
them report a different script than the one of their enclosing element.
(For top-level elements that's already possible, as that's what #source does,
but for fields inside a class, we can't easily wrap a compilation unit element
around them.)

TBR: floitsch 
(to get in before vacation, with reversion rights).

Committed: https://code.google.com/p/dart/source/detail?r=9629

[Lasse Reichstein Nielsen, 2012-07-13 11:17:09]

https://chromiumcodereview.appspot.com/10703188/diff/2001/lib/compiler/implem...
File lib/compiler/implementation/elements/elements.dart (right):

https://chromiumcodereview.appspot.com/10703188/diff/2001/lib/compiler/implem...
lib/compiler/implementation/elements/elements.dart:1060: target.type = type;
We should consider whether copying these is really necessary. At the time we
patch, most of them should be empty. 
We copy the interfaces linked list directly, without cloning it. This is only
safe because we know it's not modified later (because nobody touches the patch
library after it's been used once).

[floitsch, 2012-07-17 11:06:51]

LGTM.

https://chromiumcodereview.appspot.com/10703188/diff/2001/lib/compiler/implem...
File lib/compiler/implementation/elements/elements.dart (right):

https://chromiumcodereview.appspot.com/10703188/diff/2001/lib/compiler/implem...
lib/compiler/implementation/elements/elements.dart:420: PrefixElement
cloneTo(Element enclosing, DiagnosticListener listener) {
move closer to the fields and the constructor. (same for all other "cloneTo"
methods.

https://chromiumcodereview.appspot.com/10703188/diff/2001/lib/compiler/implem...
lib/compiler/implementation/elements/elements.dart:564: result = new
VariableListElement(cachedNode, kind, enclosing);
.node

https://chromiumcodereview.appspot.com/10703188/diff/2001/lib/compiler/implem...
lib/compiler/implementation/elements/elements.dart:1078: if (member.kind ==
ElementKind.ABSTRACT_FIELD) {
Needed?.