Update to build against libchrome-293518.

libchrome is updated from revision 271506 to 293518. This CL updates
platform2 code to build against libchrome-293518 with the following
changes:

- LOG_ERROR_REPORT is removed
  (https://codereview.chromium.org/331143007)

- StringToLowerASCII is moved to base namespace
  (https://codereview.chromium.org/448853002)

BUG=chromium:411001
CQ-DEPEND=CL:216584
CQ-DEPEND=CL:216585
CQ-DEPEND=CL:216586
CQ-DEPEND=CL:216511
CQ-DEPEND=CL:217084
CQ-DEPEND=CL:217085
TEST=Trybot run on paladin, release, and chromiumos-sdk builders.

Change-Id: I9fbdad30b3a7c79c1ec4e208664b8befea31a3ec
Reviewed-on: https://chromium-review.googlesource.com/216589
Reviewed-by: Alex Vakulenko <avakulenko@chromium.org>
Tested-by: Ben Chan <benchan@chromium.org>
Commit-Queue: Ben Chan <benchan@chromium.org>
diff --git a/chrome_browser_proxy_resolver.cc b/chrome_browser_proxy_resolver.cc
index 85646f8..e8e1a69 100644
--- a/chrome_browser_proxy_resolver.cc
+++ b/chrome_browser_proxy_resolver.cc
@@ -240,7 +240,7 @@
     }
 
     string scheme = string(token.begin(), space);
-    StringToLowerASCII(&scheme);
+    base::StringToLowerASCII(&scheme);
     // Chrome uses "socks" to mean socks4 and "proxy" to mean http.
     if (scheme == "socks")
       scheme += "4";