Refactor ZLib and Verbatim encoders.

remoting/base/compressor.h

Index: remoting/base/compressor.h
diff --git a/remoting/base/compressor.h b/remoting/base/compressor.h
index edb64f842b95a268ba3774f8d3c4ad5e72972af5..1678255e2ed729e26d77aff1f4c629b59f45e89e 100644
--- a/remoting/base/compressor.h
+++ b/remoting/base/compressor.h
@@ -25,6 +25,10 @@ class Compressor {
   };
   virtual ~Compressor() {}
 
+  // Resets all the internal state so the compressor behaves as if it
+  // was just created.
+  virtual void Reset() = 0;
+
   // Compress |input_data| with |input_size| bytes.
   //
   // |output_data| is provided by the caller and |output_size| is the