update_engine: Split Extent utils from graph_utils.

"Graph" related utils should only concern parts of the code using the
inplace generator, since other generators don't use a dependency graph.

This patch splits the Extent related utils from the graph related ones
creating a new extent_utils.h file.

BUG=None
TEST=unittest still pass.

Change-Id: I0941698b0a47a6cc222e8dc062fc54eb3cdf4de2
Reviewed-on: https://chromium-review.googlesource.com/274899
Reviewed-by: Gilad Arnold <garnold@chromium.org>
Commit-Queue: Alex Deymo <deymo@chromium.org>
Tested-by: Alex Deymo <deymo@chromium.org>
diff --git a/payload_generator/metadata.cc b/payload_generator/metadata.cc
index 77e02fa..f185465 100644
--- a/payload_generator/metadata.cc
+++ b/payload_generator/metadata.cc
@@ -18,7 +18,7 @@
 #include "update_engine/extent_ranges.h"
 #include "update_engine/payload_generator/delta_diff_generator.h"
 #include "update_engine/payload_generator/ext2_utils.h"
-#include "update_engine/payload_generator/graph_utils.h"
+#include "update_engine/payload_generator/extent_utils.h"
 #include "update_engine/payload_generator/inplace_generator.h"
 #include "update_engine/utils.h"
 
@@ -281,7 +281,7 @@
                           int ref_offset,
                           void* priv) {
   vector<Extent>* extents = static_cast<vector<Extent>*>(priv);
-  graph_utils::AppendBlockToExtents(extents, *blocknr);
+  AppendBlockToExtents(extents, *blocknr);
   return 0;
 }
 
@@ -295,7 +295,7 @@
                                void* priv) {
   vector<Extent>* extents = static_cast<vector<Extent>*>(priv);
   if (blockcnt < 0) {
-    graph_utils::AppendBlockToExtents(extents, *blocknr);
+    AppendBlockToExtents(extents, *blocknr);
   }
   return 0;
 }