Added code to disable 'paste' if nothing is present in clipboard to paste.

Source/core/editing/Editor.cpp

Index: Source/core/editing/Editor.cpp
diff --git a/Source/core/editing/Editor.cpp b/Source/core/editing/Editor.cpp
index adb58dbcd3518a79a9e837160f46bc8b12b6a29d..9a3ded5e744c4218214f7f1414458b2eab3328fb 100644
--- a/Source/core/editing/Editor.cpp
+++ b/Source/core/editing/Editor.cpp
@@ -239,7 +239,10 @@ bool Editor::canCopy() const
 
 bool Editor::canPaste() const
 {
-    return canEdit();
+    if (!canEdit())
+        return false;
+    String text = Pasteboard::generalPasteboard()->plainText();

[jamesr, 2014/07/24 18:27:15]

this is going to do a synchronous IPC to the browser process on every call,
fetch the entire paste buffer, and copy it back to the renderer just to throw
everything away but 1 bit.  This function appears to be called pretty often.  Is
there no better way to do this?

+    return !text.isEmpty();
 }
 
 bool Editor::canDelete() const