Represent tokens as a compressed stream instead of an array.

vm/raw_object.h

Index: vm/raw_object.h
===================================================================
--- vm/raw_object.h	(revision 9536)
+++ vm/raw_object.h	(working copy)
@@ -626,13 +626,13 @@
     return reinterpret_cast<RawObject**>(&ptr()->private_key_);
   }
   RawString* private_key_;  // Key used for private identifiers.
-  RawSmi* length_;  // Number of tokens.
-
+  RawSmi* length_;  // Length of token stream.
+  RawArray* token_objects_;
+  RawObject** to() {
+    return reinterpret_cast<RawObject**>(&ptr()->token_objects_);
+  }
   // Variable length data follows here.
-  RawObject* data_[0];
-  RawObject** to(intptr_t length) {
-    return reinterpret_cast<RawObject**>(&ptr()->data_[length - 1]);
-  }
+  uint8_t data_[0];
 
   friend class SnapshotReader;
 };