Remove legacy StartsWithASCII function.

extensions/common/extension.cc

Index: extensions/common/extension.cc
diff --git a/extensions/common/extension.cc b/extensions/common/extension.cc
index d42fce6a94918c42c005446c24fb9c9921e7ed99..b6803857ef917a2aacf79637f471ed28957358dc 100644
--- a/extensions/common/extension.cc
+++ b/extensions/common/extension.cc
@@ -154,7 +154,8 @@ GURL Extension::GetResourceURL(const GURL& extension_url,
     path = relative_path.substr(1);
 
   GURL ret_val = GURL(extension_url.spec() + path);
-  DCHECK(base::StartsWithASCII(ret_val.spec(), extension_url.spec(), false));
+  DCHECK(base::StartsWith(ret_val.spec(), extension_url.spec(),
+                          base::CompareCase::INSENSITIVE_ASCII));
 
   return ret_val;
 }
@@ -205,7 +206,8 @@ bool Extension::ParsePEMKeyBytes(const std::string& input,
     return false;
 
   std::string working = input;
-  if (base::StartsWithASCII(working, kKeyBeginHeaderMarker, true)) {
+  if (base::StartsWith(working, kKeyBeginHeaderMarker,
+                       base::CompareCase::SENSITIVE)) {
     working = base::CollapseWhitespaceASCII(working, true);
     size_t header_pos = working.find(kKeyInfoEndMarker,
       sizeof(kKeyBeginHeaderMarker) - 1);