Bug 1463809 - Don't lookup mimeinfo of application/octet-stream; r=Paolo

Mimeinfo returned for the generic application/octet-stream content
type is usually irrelevant to the file extension, getting mimeinfo
from extension itself is more reliable.

Also prefer file extension over application/octet-stream content tyope
when lookup in extras.

MozReview-Commit-ID: A9Q2NFAwQ7b

--HG--
extra : rebase_source : 4206cbfd898fb12b2415ef751a74d1bdeee26a2d

uriloader/exthandler/nsExternalHelperAppService.cpp

@@ -2595,16 +2595,11 @@ NS_IMETHODIMP nsExternalHelperAppService::GetFromTypeAndExtension(const nsACStri
   // (3) No match yet. Ask extras.
   if (!found) {
     rv = NS_ERROR_FAILURE;
-#ifdef XP_WIN
-    /* XXX Gross hack to wallpaper over the most common Win32
-     * extension issues caused by the fix for bug 116938.  See bug
-     * 120327, comment 271 for why this is needed.  Not even sure we
-     * want to remove this once we have fixed all this stuff to work
-     * right; any info we get from extras on this type is pretty much
-     * useless....
-     */
+    // Getting info for application/octet-stream content-type from extras
+    // does not make a sense because this tends to open all octet-streams
+    // as Binary file with exe, com or bin extension regardless the real
+    // extension.
     if (!typeToUse.Equals(APPLICATION_OCTET_STREAM, nsCaseInsensitiveCStringComparator()))
-#endif
       rv = FillMIMEInfoForMimeTypeFromExtras(typeToUse, *_retval);
     LOG(("Searched extras (by type), rv 0x%08" PRIX32 "\n", static_cast<uint32_t>(rv)));
     // If that didn't work out, try file extension from extras

uriloader/exthandler/unix/nsOSHelperAppService.cpp

@@ -31,6 +31,7 @@
 #include "prenv.h"      // for PR_GetEnv()
 #include "nsAutoPtr.h"
 #include "mozilla/Preferences.h"
+#include "nsMimeTypes.h"
 
 using namespace mozilla;
 
@@ -1450,7 +1451,12 @@ nsOSHelperAppService::GetMIMEInfoFromOS(const nsACString& aType,
                                         const nsACString& aFileExt,
                                         bool       *aFound) {
   *aFound = true;
-  RefPtr<nsMIMEInfoBase> retval = GetFromType(PromiseFlatCString(aType));
+  RefPtr<nsMIMEInfoBase> retval;
+  // Fallback to lookup by extension when generic 'application/octet-stream'
+  // content type is received.
+  if (!aType.EqualsLiteral(APPLICATION_OCTET_STREAM)) {
+    retval = GetFromType(PromiseFlatCString(aType));
+  }
   bool hasDefault = false;
   if (retval)
     retval->GetHasDefaultHandler(&hasDefault);