Move payload generator files to payload_generator/ directory.

This creates a new subdirectory payload_generator/ with all the
payload generator specific files.

The SConstruct file is updated to continue building all the files
together, including those in the subdirectories, since some parts
of the update_engine are using parts of the payload generation code.

To reduce this code coupling, a new payload_constants.h file is
introduced, with few constants used on the payload definition by both
the payload generation and the payload performer.

Finally, includes are updated and in some cases removed when they
weren't used. Order of includes is also fixed to comply with the
style guide.

BUG=chromium:374377
TEST=Build and unittests still pass. delta_generator still present on base directory.

Change-Id: I454bbc7a66c70ebb19fd596c352c7be40a081f3d
Reviewed-on: https://chromium-review.googlesource.com/200325
Reviewed-by: Alex Deymo <deymo@chromium.org>
Commit-Queue: Alex Deymo <deymo@chromium.org>
Tested-by: Alex Deymo <deymo@chromium.org>
diff --git a/delta_performer.cc b/delta_performer.cc
index 89c319d..c0932df 100644
--- a/delta_performer.cc
+++ b/delta_performer.cc
@@ -13,19 +13,18 @@
 #include <vector>
 
 #include <base/file_util.h>
+#include <base/format_macros.h>
 #include <base/memory/scoped_ptr.h>
 #include <base/strings/string_util.h>
 #include <base/strings/stringprintf.h>
-#include <base/format_macros.h>
 #include <google/protobuf/repeated_field.h>
 
 #include "update_engine/bzip_extent_writer.h"
 #include "update_engine/constants.h"
-#include "update_engine/delta_diff_generator.h"
 #include "update_engine/extent_ranges.h"
 #include "update_engine/extent_writer.h"
-#include "update_engine/graph_types.h"
 #include "update_engine/hardware_interface.h"
+#include "update_engine/payload_constants.h"
 #include "update_engine/payload_signer.h"
 #include "update_engine/payload_state_interface.h"
 #include "update_engine/prefs_interface.h"
@@ -33,10 +32,10 @@
 #include "update_engine/terminator.h"
 #include "update_engine/update_attempter.h"
 
+using google::protobuf::RepeatedPtrField;
 using std::min;
 using std::string;
 using std::vector;
-using google::protobuf::RepeatedPtrField;
 
 namespace chromeos_update_engine {