Add Clipboard::GetSequenceNumber test and fix Android.

ui/android/java/src/org/chromium/ui/base/Clipboard.java

Index: ui/android/java/src/org/chromium/ui/base/Clipboard.java
diff --git a/ui/android/java/src/org/chromium/ui/base/Clipboard.java b/ui/android/java/src/org/chromium/ui/base/Clipboard.java
index aaa500ea6dec0a58c941f9e461844608253c7c66..4724ed1deb477e281a884bde0a03b5c91554505b 100644
--- a/ui/android/java/src/org/chromium/ui/base/Clipboard.java
+++ b/ui/android/java/src/org/chromium/ui/base/Clipboard.java
@@ -27,11 +27,31 @@ public class Clipboard {
     private final ClipboardManager mClipboardManager;
 
     /**
+     * Simple helper class to proxy the clipboard change callback to C++.
+     */
+    private class Listener implements ClipboardManager.OnPrimaryClipChangedListener {

[bulach, 2014/01/14 14:45:05]

wild guess: in the test, it's doing base::RunLoop().RunUntilIdle(), which only
works for C++ based tasks...

the java-side may trigger a callback later on, without ever going through the
PostTask, MessageLoop, or hitting C++ at all.. 

also note in the test, since the call stack is _inside_ C++, the java side will
never be "pumped", so the callback would potentially never be executed...

see the "internals":
https://android.googlesource.com/platform/frameworks/base/+/b267554/core/java...

looks like it has a Handler there, so that it posts a java message to itself to
then reportPrimaryClipChanged?

could that be the case?

unfortunately, there's no easy way to integrate this that I know of.. :(

+        /** The native C++ object that receives the callback. */
+        private final long mNativeClipboardChangeListener;
+
+        private Listener(long nativeClipboardChangeListener) {
+            mNativeClipboardChangeListener = nativeClipboardChangeListener;
+        }
+
+        /**
+         * Callback that is invoked by ClipboardManager when the primary clip changes.
+         */
+        @Override
+        public void onPrimaryClipChanged() {
+            Clipboard.this.nativeOnChange(mNativeClipboardChangeListener);
+        }
+    };
+
+    /**
      * Use the factory constructor instead.
      *
      * @param context for accessing the clipboard
      */
-    public Clipboard(final Context context) {
+    private Clipboard(final Context context) {
         mContext = context;
         mClipboardManager = (ClipboardManager)
                 context.getSystemService(Context.CLIPBOARD_SERVICE);
@@ -44,7 +64,7 @@ public class Clipboard {
      * @return the new object
      */
     @CalledByNative
-    private static Clipboard create(final Context context) {
+    public static Clipboard create(final Context context) {
         return new Clipboard(context);
     }
 
@@ -153,6 +173,15 @@ public class Clipboard {
         return ApiCompatibilityUtils.isHTMLClipboardSupported();
     }
 
+    /**
+     * Adds a listener to detect when the clipboard contents change.
+     */
+    @CalledByNative
+    public void addChangeListener(long nativeClipboardChangeListener) {
+        mClipboardManager.addPrimaryClipChangedListener(
+            new Listener(nativeClipboardChangeListener));
+    }
+
     private void setPrimaryClipNoException(ClipData clip) {
         try {
             mClipboardManager.setPrimaryClip(clip);
@@ -162,4 +191,6 @@ public class Clipboard {
             Toast.makeText(mContext, text, Toast.LENGTH_SHORT).show();
         }
     }
+
+    private native void nativeOnChange(long nativeClipboardChangeListener);
 }