Fixing icu_fold_case_util.cc compilation for Jumbo builds

Compilation settings:

target_os="android"
target_cpu="arm"
enable_nacl=false
symbol_level=0
remove_webcore_debug_symbols=true
is_debug=false
dcheck_always_on=false
is_component_build=false
use_jumbo_build=true

Compilation error without patch:

./../../content/browser/font_unique_name_lookup/icu_fold_case_util.cc:7:19: error: using namespace directive in global context in header [-Werror,-Wheader-hygiene]
using namespace ::icu_62;
                  ^

Change-Id: Idd624fd0d5a14e49070c958a18a7e7136a14a659
Reviewed-on: https://chromium-review.googlesource.com/1172125
Commit-Queue: Dominik Röttsches <drott@chromium.org>
Reviewed-by: Dominik Röttsches <drott@chromium.org>
Cr-Commit-Position: refs/heads/master@{#582531}

content/browser/font_unique_name_lookup/icu_fold_case_util.cc

@@ -4,12 +4,11 @@
 
 #include "content/browser/font_unique_name_lookup/icu_fold_case_util.h"
 
-using namespace ::icu_62;
-
 namespace content {
 
 std::string IcuFoldCase(const std::string& name_request) {
-  UnicodeString name_request_unicode = UnicodeString::fromUTF8(name_request);
+  icu_62::UnicodeString name_request_unicode =
+      icu_62::UnicodeString::fromUTF8(name_request);
   name_request_unicode.foldCase();
   std::string name_request_lower;
   name_request_unicode.toUTF8String(name_request_lower);