update_engine: Update libchrome APIS to r456626.

The new libchrome has been ported from Chromium and some APIs
have changed. Make necessary changes at call sites.

BUG=chromium:724678
CQ-DEPEND=CL:480928
Test: Build.

Change-Id: I4dbaea4a2a19031375a8bf2415645a4f226dab57
diff --git a/test_http_server.cc b/test_http_server.cc
index 2955e79..93aa11c 100644
--- a/test_http_server.cc
+++ b/test_http_server.cc
@@ -98,9 +98,11 @@
   request->raw_headers = headers;
 
   // Break header into lines.
-  vector<string> lines;
-  base::SplitStringUsingSubstr(
-      headers.substr(0, headers.length() - strlen(EOL EOL)), EOL, &lines);
+  vector<string> lines = base::SplitStringUsingSubstr(
+      headers.substr(0, headers.length() - strlen(EOL EOL)),
+      EOL,
+      base::TRIM_WHITESPACE,
+      base::SPLIT_WANT_ALL);
 
   // Decode URL line.
   vector<string> terms = base::SplitString(lines[0], base::kWhitespaceASCII,