[Net] Update MIME type for .js files

According to https://html.spec.whatwg.org/multipage/scripting.html#scriptingLanguages,
JS files should have a MIME type of text/javascript. Update our mappings.

Bug: 857588

Change-Id: I6c9ce8c52a3e6afcb8768392b59e766a0db3b5c5
Reviewed-on: https://chromium-review.googlesource.com/1117564
Commit-Queue: Asanka Herath <asanka@chromium.org>
Reviewed-by: Asanka Herath <asanka@chromium.org>
Cr-Commit-Position: refs/heads/master@{#571472}

chrome/browser/extensions/extension_protocols_unittest.cc

@@ -747,8 +747,7 @@ TEST_P(ExtensionProtocolsTest, MimeTypesForKnownFiles) {
     const char* file_name;
     const char* expected_mime_type;
   } test_cases[] = {
-      {"json_file.json", "application/json"},
-      {"js_file.js", "application/javascript"},
+      {"json_file.json", "application/json"}, {"js_file.js", "text/javascript"},
   };
 
   for (const auto& test_case : test_cases) {

net/base/mime_util.cc

@@ -80,7 +80,6 @@ static const MimeInfo kPrimaryMappings[] = {
     // Must precede audio/webm .
     {"video/webm", "webm"},
 
-    {"application/javascript", "js"},
     {"application/wasm", "wasm"},
     {"application/x-chrome-extension", "crx"},
     {"application/xhtml+xml", "xhtml,xht,xhtm"},
@@ -98,6 +97,7 @@ static const MimeInfo kPrimaryMappings[] = {
     {"multipart/related", "mht,mhtml"},
     {"text/css", "css"},
     {"text/html", "html,htm,shtml,shtm"},
+    {"text/javascript", "js"},
     {"text/xml", "xml"},
     {"video/mp4", "mp4,m4v"},
     {"video/ogg", "ogv,ogm"},
@@ -110,6 +110,7 @@ static const MimeInfo kSecondaryMappings[] = {
     {"application/epub+zip", "epub"},
     {"application/font-woff", "woff"},
     {"application/gzip", "gz,tgz"},
+    {"application/javascript", "js"},
     {"application/json", "json"},  // Per http://www.ietf.org/rfc/rfc4627.txt.
     {"application/octet-stream", "bin,exe,com"},
     {"application/pdf", "pdf"},