Add script streaming API

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 eeb40e260f62727610c52c9591cb62ca231885c9..ba7720a498d6c60d8a22e8c20ae636486210e0fc 100644
--- a/src/scanner-character-streams.h
+++ b/src/scanner-character-streams.h
@@ -59,6 +59,9 @@ class Utf8ToUtf16CharacterStream: public BufferedUtf16CharacterStream {
   Utf8ToUtf16CharacterStream(const byte* data, unsigned length);
   virtual ~Utf8ToUtf16CharacterStream();
 
+  static unsigned CopyChars(uint16_t* dest, unsigned length, const byte* src,
+                            unsigned* src_pos, unsigned src_length);
+
  protected:
   virtual unsigned BufferSeekForward(unsigned delta);
   virtual unsigned FillBuffer(unsigned char_position);
@@ -73,6 +76,38 @@ class Utf8ToUtf16CharacterStream: public BufferedUtf16CharacterStream {
 };
 
 
+// ExternalStreamingStream is a wrapper around an ExternalSourceStream (see
+// include/v8.h) subclass implemented by the embedder.
+class ExternalStreamingStream : public BufferedUtf16CharacterStream {
+ public:
+  explicit ExternalStreamingStream(
+      ScriptCompiler::ExternalSourceStream* source_stream)
+      : source_stream_(source_stream),
+        current_data_(NULL),
+        current_data_offset_(0),
+        current_data_length_(0) {}
+
+  virtual ~ExternalStreamingStream() { delete[] current_data_; }
+
+  virtual unsigned BufferSeekForward(unsigned delta) V8_OVERRIDE {
+    // We never need to seek forward when streaming scripts. We only seek
+    // forward when we want to parse a function whose location we already know,
+    // and when streaming, we don't know the locations of anything we haven't
+    // seen yet.
+    UNREACHABLE();
+    return 0;
+  }
+
+  virtual unsigned FillBuffer(unsigned position);
+
+ private:
+  ScriptCompiler::ExternalSourceStream* source_stream_;
+  const char* current_data_;
+  unsigned current_data_offset_;
+  unsigned current_data_length_;
+};
+
+
 // UTF16 buffer to read characters from an external string.
 class ExternalTwoByteStringUtf16CharacterStream: public Utf16CharacterStream {
  public: