Remove legacy StartsWithASCII function.

content/child/simple_webmimeregistry_impl.cc

Index: content/child/simple_webmimeregistry_impl.cc
diff --git a/content/child/simple_webmimeregistry_impl.cc b/content/child/simple_webmimeregistry_impl.cc
index 68d87556c42c2e4c8e51b5be632613e471ee5084..a25e2aecdfb459ed56a3249cd1e267ecf9dd199e 100644
--- a/content/child/simple_webmimeregistry_impl.cc
+++ b/content/child/simple_webmimeregistry_impl.cc
@@ -42,7 +42,8 @@ WebMimeRegistry::SupportsType
     const WebString& mime_type) {
     std::string ascii_mime_type = ToASCIIOrEmpty(mime_type);
     return (mime_util::IsSupportedImageMimeType(ascii_mime_type) ||
-            (base::StartsWithASCII(ascii_mime_type, "image/", true) &&
+            (base::StartsWith(ascii_mime_type, "image/",
+                              base::CompareCase::SENSITIVE) &&
              mime_util::IsSupportedNonImageMimeType(ascii_mime_type)))
                ? WebMimeRegistry::IsSupported
                : WebMimeRegistry::IsNotSupported;