[DevTools] Support SVG file in DevTools window. [1/2 chromium]

We are using .svg file in ServiceWorkersView but the mime-type for .svg file is not correctly set.

BUG=466871

Review URL: https://codereview.chromium.org/1035873002

Cr-Commit-Position: refs/heads/master@{#322393}

chrome/browser/ui/webui/devtools_ui.cc

@@ -76,6 +76,8 @@ std::string GetMimeTypeForPath(const std::string& path) {
     return "image/png";
   } else if (EndsWith(filename, ".gif", false)) {
     return "image/gif";
+  } else if (EndsWith(filename, ".svg", false)) {
+    return "image/svg+xml";
   } else if (EndsWith(filename, ".manifest", false)) {
     return "text/cache-manifest";
   }