Include source in kernel.

pkg/kernel/binary.md

 This file describes the binary format of Dart Kernel.
 
 Notation
 --------
 Bitmasks are described with the syntax:
 ```scala
     Byte flags (flag1, flag2, ..., flagN)
 ```
 where 'flag<N>' is the N-th least significant bit,
 (so flag1 is the least significant bit).
@@ skipping 41 matching lines @@
 }
 
 type StringTable {
   List<String> strings;
 }
 
 type StringReference {
   UInt index; // Index into the StringTable strings.
 }
 
-type LineStarts {
+type LineStartsAndSource {
+  String source;
   // Line starts are delta-encoded (they are encoded as line lengths).  The list
   // [0, 10, 25, 32, 42] is encoded as [0, 10, 15, 7, 10].
   List<Uint> lineStarts;
 }
 
-type UriLineStarts {
+type UriLineStartsAndSource {
   List<String> uris;
-  LineStarts[uris.length] lineStarts;
+  LineStartsAndSource[uris.length] lineStartsAndSource;
 }
 
 type UriReference {
-  UInt index; // Index into the UriLineStarts uris.
+  UInt index; // Index into the UriLineStartsAndSource uris.
 }
 
 type FileOffset {
   // Encoded as offset + 1 to accommodate -1 indicating no offset.
   UInt fileOffset;
 }
 
 type Option<T> {
   Byte tag;
 }
 type Nothing extends Option<T> {
   Byte tag = 0;
 }
 type Something<T> extends Option<T> {
   Byte tag = 1;
   T value;
 }
 
 type ProgramFile {
   MagicWord magic = 0x90ABCDEF;
   StringTable strings;
-  UriLineStarts lineStartsMap;
+  UriLineStartsAndSource lineStartsAndSourceMap;
   List<Library> libraries;
   LibraryProcedureReference mainMethod;
 }
 
 type LibraryReference {
   // Index into the ProgramFile libraries.
   UInt index;
 }
 
 abstract type ClassReference {}
@@ skipping 788 matching lines @@
 
 /* enum BaseClassKind { None, Exact, Subclass, Subtype, } */
 
 type InferredValue {
   ClassReference baseClass; // May be NullReference if kind = None.
   Byte kind; // Index into BaseClassKind.
   Byte valueBits; // See lib/type_propagation/type_propagation.dart
 }
 
 ```