Improve regenerated source code.

runtime/vm/object.cc

Index: runtime/vm/object.cc
diff --git a/runtime/vm/object.cc b/runtime/vm/object.cc
index f5d5253bcc584f2a42acce3e5bc6e73fe4214da2..b7d6ead2191b67f513dcabb2e155638b8725aced 100644
--- a/runtime/vm/object.cc
+++ b/runtime/vm/object.cc
@@ -8144,6 +8144,16 @@ RawString* TokenStream::GenerateSource(TokenPosition start_pos,
       separator = NULL;
     } else if ((curr == Token::kSEMICOLON) && (next != Token::kNEWLINE)) {
       separator = &Symbols::Blank();
+    } else if ((curr == Token::kIS) && (next == Token::kNOT)) {
+      separator = NULL;
+    } else if ((prev == Token::kIS) && (curr == Token::kNOT)) {
+      separator = &Symbols::Blank();
+    } else if ((curr == Token::kIDENT) &&
+               ((next == Token::kINCR) || (next == Token::kDECR))) {
+      separator = NULL;
+    } else if (((curr == Token::kINCR) || (curr == Token::kDECR)) &&
+               (next == Token::kIDENT)) {
+      separator = NULL;
     }
 
     // Add the separator.