[kernel] Use helper functions to minimize assumptions about dill layout.

[kernel] Use helper functions to minimize assumptions about dill layout.

Attempt to use the helper functions to minimize the number of places
that would need updating should the binary file (the dill file) layout
change.

The changed code (in FieldHelper) makes assumptions about the layout of
the FunctionNode. Instead use FunctionNodeHelper to get the wanted data.

Also replaced an unconditional read-and-go-back with the usage of
AlternativeReadingScope.

BUG=
R=sivachandra@google.com

Committed: https://github.com/dart-lang/sdk/commit/fdd465e54062b1a19028cc5590c12d19f32e7c77

[jensj, 2017-08-02 13:16:43]

Description was changed from

==========
[kernel] Use helper functions to minimize assumptions about dill layout.

Attempt to use the helper functions to minimize the number of places
that would need updating should the binary file (the dill file) layout
change.

BUG=
==========

to

==========
[kernel] Use helper functions to minimize assumptions about dill layout.

Attempt to use the helper functions to minimize the number of places
that would need updating should the binary file (the dill file) layout
change.

The changed code (in FieldHelper) makes assumptions about the layout of
the FunctionNode. Instead use FunctionNodeHelper to get the wanted data.

Also replaced an unconditional read-and-go-back with the usage of
AlternativeReadingScope.

BUG=
==========

[jensj, 2017-08-02 13:19:14]

jensj@google.com changed reviewers:
+ sivachandra@google.com

[jensj, 2017-08-02 13:19:15]

There are probably more instances of stuff like this, I just happened to stumble
upon this one.

[sivachandra, 2017-08-02 13:26:29]

LGTM

[jensj, 2017-08-03 06:37:33]

Description was changed from

==========
[kernel] Use helper functions to minimize assumptions about dill layout.

Attempt to use the helper functions to minimize the number of places
that would need updating should the binary file (the dill file) layout
change.

The changed code (in FieldHelper) makes assumptions about the layout of
the FunctionNode. Instead use FunctionNodeHelper to get the wanted data.

Also replaced an unconditional read-and-go-back with the usage of
AlternativeReadingScope.

BUG=
==========

to

==========
[kernel] Use helper functions to minimize assumptions about dill layout.

Attempt to use the helper functions to minimize the number of places
that would need updating should the binary file (the dill file) layout
change.

The changed code (in FieldHelper) makes assumptions about the layout of
the FunctionNode. Instead use FunctionNodeHelper to get the wanted data.

Also replaced an unconditional read-and-go-back with the usage of
AlternativeReadingScope.

BUG=
R=sivachandra@google.com

Committed:
https://github.com/dart-lang/sdk/commit/fdd465e54062b1a19028cc5590c12d19f32e7c77
==========

[jensj, 2017-08-03 06:37:34]

Committed patchset #1 (id:1) manually as
fdd465e54062b1a19028cc5590c12d19f32e7c77 (presubmit successful).