Tidy ELF builder.

Don't do "if (ptr)". Use const. Use DISALLOW_COPY_AND_ASSIGN. Avoid public
member variables.
Move ValueObject to base and use in ELF builder.
Tidy VectorOutputStream to not use non-const reference arguments.

Change-Id: I2c727c3fc61769c3726de7cfb68b2d6eb4477e53
diff --git a/compiler/vector_output_stream.cc b/compiler/vector_output_stream.cc
index e5ff729..3d33673 100644
--- a/compiler/vector_output_stream.cc
+++ b/compiler/vector_output_stream.cc
@@ -20,8 +20,8 @@
 
 namespace art {
 
-VectorOutputStream::VectorOutputStream(const std::string& location, std::vector<uint8_t>& vector)
-  : OutputStream(location), offset_(vector.size()), vector_(vector) {}
+VectorOutputStream::VectorOutputStream(const std::string& location, std::vector<uint8_t>* vector)
+  : OutputStream(location), offset_(vector->size()), vector_(vector) {}
 
 off_t VectorOutputStream::Seek(off_t offset, Whence whence) {
   CHECK(whence == kSeekSet || whence == kSeekCurrent || whence == kSeekEnd) << whence;
@@ -36,7 +36,7 @@
       break;
     }
     case kSeekEnd: {
-      new_offset = vector_.size() + offset;
+      new_offset = vector_->size() + offset;
       break;
     }
   }