Fix cast exception when a Handle gets a wrong element because of name conflict.

Fix cast exception when a Handle gets a wrong element because of name conflict.

For example:

type 'TopLevelVariableElementImpl' is not a subtype of type 'FunctionTypeAliasElement' in type cast where
  TopLevelVariableElementImpl is from package:analyzer/src/dart/element/element.dart
  FunctionTypeAliasElement is from package:analyzer/dart/element/element.dart

R=brianwilkerson@google.com
BUG=

Committed: https://github.com/dart-lang/sdk/commit/0adb817be27994916cd256eb90e22ca6a6a1446b

[Brian Wilkerson, 2017-04-17 21:37:54]

lgtm

[scheglov, 2017-04-17 21:52:37]

Description was changed from

==========
Fix cast exception when a Handle gets a wrong element because of name conflict.

For example:

type 'TopLevelVariableElementImpl' is not a subtype of type
'FunctionTypeAliasElement' in type cast where
  TopLevelVariableElementImpl is from
package:analyzer/src/dart/element/element.dart
  FunctionTypeAliasElement is from package:analyzer/dart/element/element.dart

R=brianwilkerson@google.com
BUG=
==========

to

==========
Fix cast exception when a Handle gets a wrong element because of name conflict.

For example:

type 'TopLevelVariableElementImpl' is not a subtype of type
'FunctionTypeAliasElement' in type cast where
  TopLevelVariableElementImpl is from
package:analyzer/src/dart/element/element.dart
  FunctionTypeAliasElement is from package:analyzer/dart/element/element.dart

R=brianwilkerson@google.com
BUG=

Committed:
https://github.com/dart-lang/sdk/commit/0adb817be27994916cd256eb90e22ca6a6a1446b
==========

[scheglov, 2017-04-17 21:52:38]

Committed patchset #1 (id:1) manually as
0adb817be27994916cd256eb90e22ca6a6a1446b (presubmit successful).