linux: fix a layout test by having our test plugin provide two mimetypes

webkit/tools/npapi_layout_test_plugin/main.cpp

 /*
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@@ skipping 479 matching lines @@
     return NPERR_GENERIC_ERROR;
 }
 
 #if defined(OS_LINUX)
 NPError NP_GetValue(NPP instance, NPPVariable variable, void *value)
 {
     return NPP_GetValue(instance, variable, value);
 }
 
 const char* NP_GetMIMEDescription(void) {
-    return "application/x-webkit-test-netscape:testnetscape:test netscape content";
+    // The layout test LayoutTests/fast/js/navigator-mimeTypes-length.html
+    // asserts that the number of mimetypes handled by plugins should be
+    // greater than the number of plugins.  This isn't true if we're
+    // the only plugin and we only handle one mimetype, so specify
+    // multiple mimetypes here.
+    return "application/x-webkit-test-netscape:testnetscape:test netscape content;"
+           "application/x-webkit-test-netscape2:testnetscape2:test netscape content2";
 }
 #endif