ART: Track Flush & Close in FdFile

Implement a check that aborts when a file hasn't been explicitly
flushed and closed when it is destructed.

Add WARN_UNUSED to FdFile methods.

Update dex2oat, patchoat, scoped_flock and some gtests to pass with
this.

(cherry picked from commit 9433ec60b325b708b9fa87e699ab4a6565741494)

Change-Id: I9ab03b1653e69f44cc98946dc89d764c3e045dd4
diff --git a/compiler/image_test.cc b/compiler/image_test.cc
index 7e2be3e..dac1ef4 100644
--- a/compiler/image_test.cc
+++ b/compiler/image_test.cc
@@ -105,13 +105,16 @@
     ASSERT_TRUE(success_image);
     bool success_fixup = ElfWriter::Fixup(dup_oat.get(), writer->GetOatDataBegin());
     ASSERT_TRUE(success_fixup);
+
+    ASSERT_EQ(dup_oat->FlushCloseOrErase(), 0) << "Could not flush and close oat file "
+                                               << oat_file.GetFilename();
   }
 
   {
     std::unique_ptr<File> file(OS::OpenFileForReading(image_file.GetFilename().c_str()));
     ASSERT_TRUE(file.get() != NULL);
     ImageHeader image_header;
-    file->ReadFully(&image_header, sizeof(image_header));
+    ASSERT_EQ(file->ReadFully(&image_header, sizeof(image_header)), true);
     ASSERT_TRUE(image_header.IsValid());
     ASSERT_GE(image_header.GetImageBitmapOffset(), sizeof(image_header));
     ASSERT_NE(0U, image_header.GetImageBitmapSize());