bug 773943 - fix null pointer exception from accessing getExternalFilesDir r=snorp

mobile/android/base/GeckoApp.java

@@ -2374,19 +2374,20 @@ abstract public class GeckoApp
         ((GeckoApplication) getApplication()).removeApplicationLifecycleCallbacks(this);
     }
 
-    // Get/Create a temporary direcory
+    // Get a temporary directory, may return null
     public static File getTempDirectory() {
         File dir = mAppContext.getExternalFilesDir("temp");
-        dir.mkdirs();
         return dir;
     }
 
     // Delete any files in our temporary directory
     public static void deleteTempFiles() {
-        File[] files  = getTempDirectory().listFiles();
+        File dir = getTempDirectory();
+        if (dir == null)
+            return;
+        File[] files = dir.listFiles();
         if (files == null)
             return;
-
         for (File file : files) {
             file.delete();
         }

mobile/android/base/GeckoAppShell.java

@@ -1042,8 +1042,13 @@ public class GeckoAppShell
         Intent intent = new Intent(Intent.ACTION_SEND);
         boolean isDataURI = aSrc.startsWith("data:");
         OutputStream os = null;
-
         File dir = GeckoApp.getTempDirectory();
+
+        if (dir == null) {
+            showImageShareFailureToast();
+            return;
+        }
+
         GeckoApp.deleteTempFiles();
 
         try {
@@ -1089,11 +1094,7 @@ public class GeckoAppShell
                intent.putExtra(Intent.EXTRA_TEXT, aSrc);
                intent.setType("text/plain");
             } else {
-               // Don't fail silently, tell the user that we weren't able to share the image
-               Toast toast = Toast.makeText(GeckoApp.mAppContext,
-                                            GeckoApp.mAppContext.getResources().getString(R.string.share_image_failed),
-                                            Toast.LENGTH_SHORT);
-               toast.show();
+               showImageShareFailureToast();
                return;
             }
         } finally {
@@ -1103,6 +1104,14 @@ public class GeckoAppShell
                 GeckoApp.mAppContext.getResources().getString(R.string.share_title)));
     }
 
+    // Don't fail silently, tell the user that we weren't able to share the image
+    private static final void showImageShareFailureToast() {
+        Toast toast = Toast.makeText(GeckoApp.mAppContext,
+                                     GeckoApp.mAppContext.getResources().getString(R.string.share_image_failed),
+                                     Toast.LENGTH_SHORT);
+        toast.show();
+    }
+
     static boolean openUriExternal(String aUriSpec, String aMimeType, String aPackageName,
                                    String aClassName, String aAction, String aTitle) {
         Intent intent = getIntentForActionString(aAction);