Modify extension request IPC messages to pass a ListValue instead of a string.

base/values.h

Index: base/values.h
diff --git a/base/values.h b/base/values.h
index 8e3669b5dcdf018b9827df8f3c439e1a60cbc9b3..b3c380c104890d40b2c4f0a6a42a32974cd771f0 100644
--- a/base/values.h
+++ b/base/values.h
@@ -171,7 +171,7 @@ class BinaryValue: public Value {
   // factory method creates a new BinaryValue by copying the contents of the
   // buffer that's passed in.
   // Returns NULL if buffer is NULL.
-  static BinaryValue* CreateWithCopiedBuffer(char* buffer, size_t size);
+  static BinaryValue* CreateWithCopiedBuffer(const char* buffer, size_t size);
 
   ~BinaryValue();
 
@@ -181,6 +181,7 @@ class BinaryValue: public Value {
 
   size_t GetSize() const { return size_; }
   char* GetBuffer() { return buffer_; }
+  const char* GetBuffer() const { return buffer_; }
 
  private:
   // Constructor is private so that only objects with valid buffer pointers