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/payload_signer_unittest.cc b/payload_signer_unittest.cc
index 2ee58f5..ff31f02 100644
--- a/payload_signer_unittest.cc
+++ b/payload_signer_unittest.cc
@@ -26,22 +26,22 @@
   // Some data and its corresponding signature:
   const string kDataToSign = "This is some data to sign.";
   const char kExpectedSignature[] = {
-    0x00, 0x8d, 0x20, 0x22, 0x87, 0xd3, 0xd0, 0xeb,
-    0x85, 0x80, 0xde, 0x76, 0xa4, 0x5a, 0xac, 0xdc,
-    0xa8, 0xe0, 0x6e, 0x10, 0x98, 0xc3, 0xa4, 0x55,
-    0x48, 0xbf, 0x15, 0x98, 0x32, 0xda, 0xbe, 0x21,
-    0x3d, 0xa8, 0x1a, 0xb6, 0xf9, 0x93, 0x03, 0x70,
-    0x44, 0x1b, 0xec, 0x39, 0xe3, 0xd4, 0xfd, 0x6b,
-    0xff, 0x84, 0xee, 0x60, 0xbe, 0xed, 0x9e, 0x5b,
-    0xac, 0xd5, 0xd6, 0x1a, 0xf9, 0x4e, 0xdb, 0x6d,
-    0x11, 0x9e, 0x01, 0xb1, 0xcb, 0x55, 0x05, 0x52,
-    0x8c, 0xad, 0xb6, 0x8e, 0x9f, 0xf7, 0xc2, 0x1a,
-    0x26, 0xb3, 0x96, 0xd2, 0x4a, 0xfd, 0x7c, 0x96,
-    0x53, 0x38, 0x3a, 0xcf, 0xab, 0x95, 0x83, 0xbd,
-    0x8e, 0xe1, 0xbd, 0x07, 0x12, 0xa2, 0x80, 0x18,
-    0xca, 0x64, 0x91, 0xee, 0x9d, 0x9d, 0xe3, 0x69,
-    0xc0, 0xab, 0x1b, 0x75, 0x9f, 0xf0, 0x64, 0x74,
-    0x01, 0xb3, 0x49, 0xea, 0x87, 0x63, 0x04, 0x29
+    0xa4, 0xbc, 0x8f, 0xeb, 0x81, 0x05, 0xaa, 0x56,
+    0x1b, 0x56, 0xe5, 0xcb, 0x9b, 0x1a, 0x00, 0xd7,
+    0x1d, 0x87, 0x8e, 0xda, 0x5e, 0x90, 0x09, 0xb8,
+    0x15, 0xf4, 0x25, 0x97, 0x2f, 0x3c, 0xa1, 0xf3,
+    0x02, 0x75, 0xcd, 0x67, 0x4b, 0x0c, 0x1f, 0xf5,
+    0x6e, 0xf1, 0x58, 0xd7, 0x0d, 0x8c, 0x18, 0x91,
+    0x52, 0x30, 0x98, 0x64, 0x58, 0xc0, 0xe2, 0xb5,
+    0x77, 0x3b, 0x96, 0x8f, 0x05, 0xc4, 0x7f, 0x7a,
+    0x9a, 0x44, 0x0f, 0xc7, 0x1b, 0x90, 0x83, 0xf8,
+    0x69, 0x05, 0xa8, 0x02, 0x57, 0xcd, 0x2e, 0x5b,
+    0x96, 0xc7, 0x77, 0xa6, 0x1f, 0x97, 0x97, 0x05,
+    0xb3, 0x30, 0x1c, 0x27, 0xd7, 0x2d, 0x31, 0x60,
+    0x84, 0x7e, 0x99, 0x00, 0xe6, 0xe1, 0x39, 0xa6,
+    0xf3, 0x3a, 0x72, 0xba, 0xc4, 0xfe, 0x68, 0xa9,
+    0x08, 0xfa, 0xbc, 0xa8, 0x44, 0x66, 0xa0, 0x60,
+    0xde, 0xc9, 0xb2, 0xba, 0xbc, 0x80, 0xb5, 0x55
   };
 
   string data_path;