From https://bugzilla.mozilla.org/show_bug.cgi?id=611953
Patch 1 - Use MOZ_APP_LAUNCHER for default browser executable (v3, un-bitrotted)


diff --git a/browser/components/shell/src/nsGNOMEShellService.cpp b/browser/components/shell/src/nsGNOMEShellService.cpp
--- a/browser/components/shell/src/nsGNOMEShellService.cpp
+++ b/browser/components/shell/src/nsGNOMEShellService.cpp
@@ -115,16 +115,19 @@ nsGNOMEShellService::Init()
 
   if (!gconf)
     return NS_ERROR_NOT_AVAILABLE;
 
   // Check G_BROKEN_FILENAMES.  If it's set, then filenames in glib use
   // the locale encoding.  If it's not set, they use UTF-8.
   mUseLocaleFilenames = PR_GetEnv("G_BROKEN_FILENAMES") != nsnull;
 
+  if (GetAppPathFromLauncher())
+    return NS_OK;
+
   nsCOMPtr<nsIProperties> dirSvc
     (do_GetService("@mozilla.org/file/directory_service;1"));
   NS_ENSURE_TRUE(dirSvc, NS_ERROR_NOT_AVAILABLE);
 
   nsCOMPtr<nsILocalFile> appPath;
   rv = dirSvc->Get(NS_XPCOM_CURRENT_PROCESS_DIR, NS_GET_IID(nsILocalFile),
                    getter_AddRefs(appPath));
   NS_ENSURE_SUCCESS(rv, rv);
@@ -133,16 +136,44 @@ nsGNOMEShellService::Init()
   NS_ENSURE_SUCCESS(rv, rv);
 
   return appPath->GetNativePath(mAppPath);
 }
 
 NS_IMPL_ISUPPORTS1(nsGNOMEShellService, nsIShellService)
 
 PRBool
+nsGNOMEShellService::GetAppPathFromLauncher()
+{
+  gchar *tmp;
+
+  const char *launcher = PR_GetEnv("MOZ_APP_LAUNCHER");
+  if (!launcher)
+    return PR_FALSE;
+
+  if (g_path_is_absolute(launcher)) {
+    mAppPath = launcher;
+    tmp = g_path_get_basename(launcher);
+    gchar *fullpath = g_find_program_in_path(tmp);
+    if (fullpath && mAppPath.Equals(fullpath))
+      mAppIsInPath = PR_TRUE;
+    g_free(fullpath);
+  } else {
+    tmp = g_find_program_in_path(launcher);
+    if (!tmp)
+      return PR_FALSE;
+    mAppPath = tmp;
+    mAppIsInPath = PR_TRUE;
+  }
+
+  g_free(tmp);
+  return PR_TRUE;
+}
+
+PRBool
 nsGNOMEShellService::KeyMatchesAppName(const char *aKeyValue) const
 {
 
   gchar *commandPath;
   if (mUseLocaleFilenames) {
     gchar *nativePath = g_filename_from_utf8(aKeyValue, -1, NULL, NULL, NULL);
     if (!nativePath) {
       NS_ERROR("Error converting path to filesystem encoding");
@@ -210,18 +241,28 @@ nsGNOMEShellService::SetDefaultBrowser(P
 {
 #ifdef DEBUG
   if (aForAllUsers)
     NS_WARNING("Setting the default browser for all users is not yet supported");
 #endif
 
   nsCOMPtr<nsIGConfService> gconf = do_GetService(NS_GCONFSERVICE_CONTRACTID);
   if (gconf) {
-    nsCAutoString appKeyValue(mAppPath);
-    appKeyValue.Append(" \"%s\"");
+    nsCAutoString appKeyValue;
+    if(mAppIsInPath) {
+      // mAppPath is in the users path, so use only the basename as the launcher
+      gchar *tmp = g_path_get_basename(mAppPath.get());
+      appKeyValue = tmp;
+      g_free(tmp);
+    } else {
+      appKeyValue = mAppPath;
+    }
+
+    appKeyValue.AppendLiteral(" %s");
+
     for (unsigned int i = 0; i < NS_ARRAY_LENGTH(appProtocols); ++i) {
       if (appProtocols[i].essential || aClaimAllTypes) {
         gconf->SetAppForProtocol(nsDependentCString(appProtocols[i].name),
                                  appKeyValue);
       }
     }
   }
 
diff --git a/browser/components/shell/src/nsGNOMEShellService.h b/browser/components/shell/src/nsGNOMEShellService.h
--- a/browser/components/shell/src/nsGNOMEShellService.h
+++ b/browser/components/shell/src/nsGNOMEShellService.h
@@ -38,26 +38,28 @@
 #define nsgnomeshellservice_h____
 
 #include "nsIShellService.h"
 #include "nsStringAPI.h"
 
 class nsGNOMEShellService : public nsIShellService
 {
 public:
-  nsGNOMEShellService() : mCheckedThisSession(PR_FALSE) { }
+  nsGNOMEShellService() : mCheckedThisSession(PR_FALSE), mAppIsInPath(PR_FALSE) { }
 
   NS_DECL_ISUPPORTS
   NS_DECL_NSISHELLSERVICE
 
   nsresult Init() NS_HIDDEN;
 
 private:
   ~nsGNOMEShellService() {}
 
   NS_HIDDEN_(PRBool) KeyMatchesAppName(const char *aKeyValue) const;
 
+  NS_HIDDEN_(PRBool) GetAppPathFromLauncher();
   PRPackedBool mCheckedThisSession;
   PRPackedBool mUseLocaleFilenames;
   nsCString    mAppPath;
+  PRPackedBool mAppIsInPath;
 };
 
 #endif // nsgnomeshellservice_h____