--- a/netwerk/protocol/http/nsHttpHandler.cpp
+++ b/netwerk/protocol/http/nsHttpHandler.cpp
@@ -286,17 +286,21 @@ nsHttpHandler::Init()
 
     mMisc.AssignLiteral("rv:" MOZILLA_UAVERSION);
 
     nsCOMPtr<nsIXULAppInfo> appInfo =
         do_GetService("@mozilla.org/xre/app-info;1");
 
     mAppName.AssignLiteral(MOZ_APP_UA_NAME);
     if (mAppName.Length() == 0 && appInfo) {
-        appInfo->GetName(mAppName);
+        // Try to get the UA name from appInfo, falling back to the name
+        appInfo->GetUAName(mAppName);
+        if (mAppName.Length() == 0) {
+          appInfo->GetName(mAppName);
+        }
         appInfo->GetVersion(mAppVersion);
         mAppName.StripChars(" ()<>@,;:\\\"/[]?={}");
     } else {
         mAppVersion.AssignLiteral(MOZ_APP_UA_VERSION);
     }
 
 #if DEBUG
     // dump user agent prefs

--- a/toolkit/xre/nsAppData.cpp
+++ b/toolkit/xre/nsAppData.cpp
@@ -86,16 +86,20 @@ ScopedAppData::ScopedAppData(const nsXRE
     SetStrongPtr(this->xreDirectory, aAppData->xreDirectory);
     SetAllocatedString(this->minVersion, aAppData->minVersion);
     SetAllocatedString(this->maxVersion, aAppData->maxVersion);
   }
 
   if (aAppData->size > offsetof(nsXREAppData, crashReporterURL)) {
     SetAllocatedString(this->crashReporterURL, aAppData->crashReporterURL);
   }
+
+  if (aAppData->size > offsetof(nsXREAppData, UAName)) {
+    SetAllocatedString(this->UAName, aAppData->UAName);
+  }
 }
 
 ScopedAppData::~ScopedAppData()
 {
   SetAllocatedString(this->vendor, nsnull);
   SetAllocatedString(this->name, nsnull);
   SetAllocatedString(this->version, nsnull);
   SetAllocatedString(this->buildID, nsnull);
@@ -105,16 +109,17 @@ ScopedAppData::~ScopedAppData()
 
   NS_IF_RELEASE(this->directory);
 
   SetStrongPtr(this->xreDirectory, (nsILocalFile*) nsnull);
   SetAllocatedString(this->minVersion, nsnull);
   SetAllocatedString(this->maxVersion, nsnull);
 
   SetAllocatedString(this->crashReporterURL, nsnull);
+  SetAllocatedString(this->UAName, nsnull);
 }
 
 nsresult
 XRE_CreateAppData(nsILocalFile* aINIFile, nsXREAppData **aAppData)
 {
   NS_ENSURE_ARG(aINIFile && aAppData);
 
   nsAutoPtr<ScopedAppData> data(new ScopedAppData());
@@ -239,16 +244,24 @@ XRE_ParseAppData(nsILocalFile* aINIFile,
     ReadStrings(parser, strings3);
     ReadFlag flags2[] = {
       { "Crash Reporter", "Enabled", NS_XRE_ENABLE_CRASH_REPORTER },
       { nsnull }
     };
     ReadFlags(parser, flags2, &aAppData->flags);
   }
 
+  if (aAppData->size > offsetof(nsXREAppData, UAName)) {
+    ReadString strings4[] = {
+      { "App", "UAName",    &aAppData->UAName },
+      { nsnull }
+    };
+    ReadStrings(parser, strings4);
+  }
+
   return NS_OK;
 }
 
 void
 XRE_FreeAppData(nsXREAppData *aAppData)
 {
   if (!aAppData) {
     NS_ERROR("Invalid arg");

--- a/toolkit/xre/nsAppRunner.cpp
+++ b/toolkit/xre/nsAppRunner.cpp
@@ -709,16 +709,28 @@ NS_IMETHODIMP
 nsXULAppInfo::GetPlatformBuildID(nsACString& aResult)
 {
   aResult.Assign(gToolkitBuildID);
 
   return NS_OK;
 }
 
 NS_IMETHODIMP
+nsXULAppInfo::GetUAName(nsACString& aResult)
+{
+  if (XRE_GetProcessType() == GeckoProcessType_Content) {
+    NS_WARNING("Attempt to get unavailable information in content process.");
+    return NS_ERROR_NOT_AVAILABLE;
+  }
+  aResult.Assign(gAppData->UAName);
+
+  return NS_OK;
+}
+
+NS_IMETHODIMP
 nsXULAppInfo::GetLogConsoleErrors(bool *aResult)
 {
   *aResult = gLogConsoleErrors;
   return NS_OK;
 }
 
 NS_IMETHODIMP
 nsXULAppInfo::SetLogConsoleErrors(bool aValue)

--- a/xpcom/build/nsXREAppData.h
+++ b/xpcom/build/nsXREAppData.h
@@ -143,16 +143,21 @@ struct nsXREAppData
    *   UAppData = $HOME[/$vendor]/$name
    *
    * If present, the 'profile' string will be used instead of the combination of
    * vendor and name as follows:
    *
    *   UAppData = $HOME/$profile
    */
   const char *profile;
+
+  /**
+   * The application name to use in the User Agent string.
+   */
+  const char *UAName;
 };
 
 /**
  * Indicates whether or not the profile migrator service may be
  * invoked at startup when creating a profile.
  */
 #define NS_XRE_ENABLE_PROFILE_MIGRATOR (1 << 1)
 

--- a/xpcom/system/nsIXULAppInfo.idl
+++ b/xpcom/system/nsIXULAppInfo.idl
@@ -81,9 +81,15 @@ interface nsIXULAppInfo : nsISupports
    * The version of the XULRunner platform.
    */
   readonly attribute ACString platformVersion;
 
   /**
    * The build ID/date of gecko and the XULRunner platform.
    */
   readonly attribute ACString platformBuildID;
+  
+  /**
+   * @see nsXREAppData.UAName
+   * @returns an empty string if nsXREAppData.UAName is not set.
+   */
+  readonly attribute ACString UAName;
 };