Remove grab-bag includes of v8.h from everywhere.

src/scanner-character-streams.h

Index: src/scanner-character-streams.h
diff --git a/src/scanner-character-streams.h b/src/scanner-character-streams.h
index 582165710db84c1171f74a163e3dcfdeaa8170ac..352e17612eaf55fd279a83774b60bd55975ee7ec 100644
--- a/src/scanner-character-streams.h
+++ b/src/scanner-character-streams.h
@@ -5,11 +5,16 @@
 #ifndef V8_SCANNER_CHARACTER_STREAMS_H_
 #define V8_SCANNER_CHARACTER_STREAMS_H_
 
+#include "src/handles.h"
 #include "src/scanner.h"
+#include "src/vector.h"
 
 namespace v8 {
 namespace internal {
 
+// Forward declarations.
+class ExternalTwoByteString;
+
 // A buffered character stream based on a random access character
 // source (ReadBlock can be called with pos_ pointing to any position,
 // even positions before the current).