Add Clipboard::GetSequenceNumber test and fix Android.

ui/base/clipboard/clipboard_unittest.cc

Index: ui/base/clipboard/clipboard_unittest.cc
diff --git a/ui/base/clipboard/clipboard_unittest.cc b/ui/base/clipboard/clipboard_unittest.cc
index 5ddec420e180aae395fca493fa3f42d1a0f77fd6..3875bd76b39ba2b7d5804e0f1290564f42c5d982 100644
--- a/ui/base/clipboard/clipboard_unittest.cc
+++ b/ui/base/clipboard/clipboard_unittest.cc
@@ -10,6 +10,7 @@
 #include "base/memory/scoped_ptr.h"
 #include "base/message_loop/message_loop.h"
 #include "base/pickle.h"
+#include "base/run_loop.h"
 #include "base/strings/string_util.h"
 #include "base/strings/utf_string_conversions.h"
 #include "testing/gtest/include/gtest/gtest.h"
@@ -717,6 +718,28 @@ TEST_F(ClipboardTest, WriteEverything) {
   // Passes if we don't crash.
 }
 
+// Simple test that the sequence number appears to change when the clipboard is
+// written to.
+// TODO(dcheng): Add a version to test CLIPBOARD_TYPE_SELECTION.
+TEST_F(ClipboardTest, GetSequenceNumber) {
+  const uint64 first_sequence_number =
+      clipboard().GetSequenceNumber(CLIPBOARD_TYPE_COPY_PASTE);
+
+  {
+    ScopedClipboardWriter writer(&clipboard(), CLIPBOARD_TYPE_COPY_PASTE);
+    writer.WriteText(UTF8ToUTF16("World"));
+  }
+
+  // On some platforms, the sequence number is updated by a UI callback so pump
+  // the message loop to make sure we get the notification.
+  base::RunLoop().RunUntilIdle();
+
+  const uint64 second_sequence_number =
+      clipboard().GetSequenceNumber(CLIPBOARD_TYPE_COPY_PASTE);
+
+  EXPECT_NE(first_sequence_number, second_sequence_number);

[raymes, 2014/01/14 02:55:47]

It might be worth checking the case that I fixed (where the number of elements
on the clipboard doesn't change resulting in a duplicate sequence number).

+}
+
 #if defined(OS_ANDROID)
 
 // Test that if another application writes some text to the pasteboard the