AU: Switch from SHA-1 to SHA-256 hash.

For hashing of images, expect a new "sha256" attribute in Omaha's updatecheck
response.

BUG=6580
TEST=unit tests, gmerged on device and updated with upgraded dev server

Change-Id: I122e21cd7edc74695cb81b2eee5ce70f152f5270

Review URL: http://codereview.chromium.org/3419018
diff --git a/omaha_request_action.cc b/omaha_request_action.cc
index c931065..cb9cd63 100644
--- a/omaha_request_action.cc
+++ b/omaha_request_action.cc
@@ -405,7 +405,7 @@
       XmlGetProperty(updatecheck_node, "DisplayVersion");
   output_object.codebase = XmlGetProperty(updatecheck_node, "codebase");
   output_object.more_info_url = XmlGetProperty(updatecheck_node, "MoreInfo");
-  output_object.hash = XmlGetProperty(updatecheck_node, "hash");
+  output_object.hash = XmlGetProperty(updatecheck_node, "sha256");
   output_object.size = ParseInt(XmlGetProperty(updatecheck_node, "size"));
   output_object.needs_admin =
       XmlGetProperty(updatecheck_node, "needsadmin") == "true";