Remove OatWriter buffering to memory for ElfWriterQuick

This allows the oat contents to be directly written to the file.

Change-Id: Ibc7ddf57477b152f07784b52f7334be73fd22833
diff --git a/compiler/driver/compiler_driver.h b/compiler/driver/compiler_driver.h
index 1799057..f3f72dd 100644
--- a/compiler/driver/compiler_driver.h
+++ b/compiler/driver/compiler_driver.h
@@ -39,6 +39,7 @@
 class AOTCompilationStats;
 class ParallelCompilationManager;
 class DexCompilationUnit;
+class OatWriter;
 class TimingLogger;
 
 enum CompilerBackend {
@@ -192,7 +193,7 @@
   bool WriteElf(const std::string& android_root,
                 bool is_host,
                 const std::vector<const DexFile*>& dex_files,
-                std::vector<uint8_t>& oat_contents,
+                OatWriter& oat_writer,
                 File* file);
 
   // TODO: move to a common home for llvm helpers once quick/portable are merged