Reland regexp global optimizations.

src/unicode.h

Index: src/unicode.h
diff --git a/src/unicode.h b/src/unicode.h
index 94ab1b4c1e7793cc1b0879e6906bb0b44851143c..91b16c9f3564f4f0fbb0846381ef02028b773f12 100644
--- a/src/unicode.h
+++ b/src/unicode.h
@@ -201,6 +201,7 @@ class CharacterStream {
 
  protected:
   virtual void FillBuffer() = 0;
+  virtual bool BoundsCheck(unsigned offset) = 0;
   // The number of characters left in the current buffer
   unsigned remaining_;
   // The current offset within the buffer
@@ -228,6 +229,9 @@ class InputBuffer : public CharacterStream {
   InputBuffer() { }
   explicit InputBuffer(Input input) { Reset(input); }
   virtual void FillBuffer();
+  virtual bool BoundsCheck(unsigned offset) {
+    return (buffer_ != util_buffer_) || (offset < kSize);
+  }
 
   // A custom offset that can be used by the string implementation to
   // mark progress within the encoded string.