Move MatchPattern to its own header and the base namespace.

extensions/shell/common/shell_content_client_unittest.cc

Index: extensions/shell/common/shell_content_client_unittest.cc
diff --git a/extensions/shell/common/shell_content_client_unittest.cc b/extensions/shell/common/shell_content_client_unittest.cc
index bf5779f7cf5bb685d1c938171308d60bd2ec9b82..eb9694dabe6ebac123df64715a2e3baa654612e9 100644
--- a/extensions/shell/common/shell_content_client_unittest.cc
+++ b/extensions/shell/common/shell_content_client_unittest.cc
@@ -6,6 +6,7 @@
 
 #include <string>
 
+#include "base/strings/pattern.h"
 #include "base/strings/string_util.h"
 #include "testing/gtest/include/gtest/gtest.h"
 
@@ -23,7 +24,7 @@ TEST_F(ShellContentClientTest, UserAgentFormat) {
       << user_agent;
 
   // Must contain a substring like "Chrome/1.2.3.4".
-  EXPECT_TRUE(MatchPattern(user_agent, "*Chrome/*.*.*.*")) << user_agent;
+  EXPECT_TRUE(base::MatchPattern(user_agent, "*Chrome/*.*.*.*")) << user_agent;
 }
 
 }  // namespace extensions