Add quotes around strings when generating source from the token stream.

vm/object.h

Index: vm/object.h
===================================================================
--- vm/object.h	(revision 9534)
+++ vm/object.h	(working copy)
@@ -3221,6 +3221,8 @@
                    intptr_t src_offset,
                    intptr_t len);
 
+  static RawString* EscapeDoubleQuotes(const String& str);
+
   static RawString* Concat(const String& str1,
                            const String& str2,
                            Heap::Space space = Heap::kNew);
@@ -3292,6 +3294,8 @@
     return kOneByteChar;
   }
 
+  RawOneByteString* EscapeDoubleQuotes() const;
+
   static intptr_t data_offset() { return OFFSET_OF(RawOneByteString, data_); }
 
   static intptr_t InstanceSize() {
@@ -3351,6 +3355,8 @@
     return kTwoByteChar;
   }
 
+  RawTwoByteString* EscapeDoubleQuotes() const;
+
   static intptr_t InstanceSize() {
     ASSERT(sizeof(RawTwoByteString) == OFFSET_OF(RawTwoByteString, data_));
     return 0;
@@ -3404,6 +3410,8 @@
     return kFourByteChar;
   }
 
+  RawFourByteString* EscapeDoubleQuotes() const;
+
   static intptr_t InstanceSize() {
     ASSERT(sizeof(RawFourByteString) == OFFSET_OF(RawFourByteString, data_));
     return 0;