Fix build issues in base/ for Android x64

This CL fixes several issues when building files under base/ for
Android x64.

BUG=346626

Review URL: https://codereview.chromium.org/179373003

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@254124 0039d316-1c4b-4281-b951-d872f2087c98


CrOS-Libchrome-Original-Commit: f690ed9164c29b905495632fa61fe17981fd7f51
diff --git a/base/json/json_writer.cc b/base/json/json_writer.cc
index efe57ec..d14c92c 100644
--- a/base/json/json_writer.cc
+++ b/base/json/json_writer.cc
@@ -96,10 +96,10 @@
       // The JSON spec requires that non-integer values in the range (-1,1)
       // have a zero before the decimal point - ".52" is not valid, "0.52" is.
       if (real[0] == '.') {
-        real.insert(0U, 1U, '0');
+        real.insert(static_cast<size_t>(0), static_cast<size_t>(1), '0');
       } else if (real.length() > 1 && real[0] == '-' && real[1] == '.') {
         // "-.1" bad "-0.1" good
-        real.insert(1U, 1U, '0');
+        real.insert(static_cast<size_t>(1), static_cast<size_t>(1), '0');
       }
       json_string_->append(real);
       return result;