Bug 850318 - Avoid blocking the UI thread on the background thread when calling getClipboardText. r=wesj

mobile/android/base/GeckoAppShell.java

@@ -1110,41 +1110,51 @@ public class GeckoAppShell
         return intent;
     }
 
-    static SynchronousQueue<String> sClipboardQueue =
-        new SynchronousQueue<String>();
-    private static String EMPTY_STRING = new String();
-
-    // On some devices, access to the clipboard service needs to happen
-    // on a thread with a looper, so dispatch this to our looper thread
-    // Note: the main looper won't work because it may be blocked on the
-    // gecko thread, which is most likely this thread
-    static String getClipboardText() {
-        ThreadUtils.postToBackgroundThread(new Runnable() {
-            @Override
+    /* On some devices, access to the clipboard service needs to happen
+     * on a thread with a looper, so this function requires a looper is
+     * present on the thread. */
     @SuppressWarnings("deprecation")
-            public void run() {
+    private static String getClipboardTextImpl() {
         Context context = GeckoApp.mAppContext;
-                String text = null;
         if (android.os.Build.VERSION.SDK_INT >= 11) {
-                    android.content.ClipboardManager cm = (android.content.ClipboardManager)
-                        context.getSystemService(Context.CLIPBOARD_SERVICE);
+            android.content.ClipboardManager cm = (android.content.ClipboardManager)context.getSystemService(Context.CLIPBOARD_SERVICE);
             if (cm.hasPrimaryClip()) {
                 ClipData clip = cm.getPrimaryClip();
                 if (clip != null) {
                     ClipData.Item item = clip.getItemAt(0);
-                            text = item.coerceToText(context).toString();
+                    return item.coerceToText(context).toString();
                 }
             }
         } else {
-                    android.text.ClipboardManager cm = (android.text.ClipboardManager)
-                        context.getSystemService(Context.CLIPBOARD_SERVICE);
-                    if (cm.hasText())
-                        text = cm.getText().toString();
+            android.text.ClipboardManager cm = (android.text.ClipboardManager)context.getSystemService(Context.CLIPBOARD_SERVICE);
+            if (cm.hasText()) {
+                return cm.getText().toString();
             }
+        }
+        return null;
+    }
+
+    private static SynchronousQueue<String> sClipboardQueue = new SynchronousQueue<String>();
+    private static String EMPTY_STRING = new String();
+
+    static String getClipboardText() {
+        // If we're on the UI thread or the background thread, we have a looper on the thread
+        // and can just call this directly. For any other threads, post the call to the
+        // background thread.
+
+        if (ThreadUtils.isOnUiThread() || ThreadUtils.isOnBackgroundThread()) {
+            return getClipboardTextImpl();
+        }
+
+        ThreadUtils.postToBackgroundThread(new Runnable() { 
+            @Override
+            public void run() {
+                String text = getClipboardTextImpl();
                 try {
                     sClipboardQueue.put(text != null ? text : EMPTY_STRING);
                 } catch (InterruptedException ie) {}
-            }});
+            }
+        });
         try {
             String ret = sClipboardQueue.take();
             return (EMPTY_STRING.equals(ret) ? null : ret);
@@ -1167,7 +1177,8 @@ public class GeckoAppShell
                         context.getSystemService(Context.CLIPBOARD_SERVICE);
                     cm.setText(text);
                 }
-            }});
+            }
+        });
     }
 
     public static void setNotificationClient(NotificationClient client) {

mobile/android/base/util/ThreadUtils.java

@@ -84,6 +84,10 @@ public final class ThreadUtils {
         return isOnThread(getUiThread());
     }
 
+    public static boolean isOnBackgroundThread() {
+        return isOnThread(sBackgroundThread);
+    }
+
     public static boolean isOnThread(Thread thread) {
         return (Thread.currentThread().getId() == thread.getId());
     }