don't hit NOTREACHED when pasting on non-x11 non-chromeos unix builds

content/renderer/webclipboard_impl.cc

 // Copyright (c) 2013 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "content/renderer/webclipboard_impl.h"
 
 #include "base/logging.h"
 #include "base/pickle.h"
 #include "base/strings/string_util.h"
 #include "base/strings/utf_string_conversions.h"
@@ skipping 194 matching lines @@
     case BufferSelection:
 #if defined(USE_X11)
 #if defined(OS_CHROMEOS)
       //  Chrome OS only supports the standard clipboard,
       //  but not the X selection clipboad.
       return false;
 #else
       *result = ui::CLIPBOARD_TYPE_SELECTION;
       break;
 #endif
 #endif

[spang, 2014/04/08 22:57:21]

This code can preprocess to 

    case BufferSelection:
    default:
      NOTREACHED();
      return false;

That seems rather unexpected. Especially since there's no "fallthrough" comment
here.

[rjkroege, 2014/04/09 14:56:07]

I'm with spang here. Why does this code not fire on Windows or Mac etc.?  Is it
possible that somewhere up the calling chain, there is a missing #ifdef that
makes sure that buffer is set to BufferStandard on embedded=1 builds?

[Mostyn Bramley-Moore, 2014/04/09 18:40:28]

X is the only platform I know of that copies on selection (I assume that's what
BufferSelection means: "the buffer was filled automatically by selection").

This is only triggered if EditingBehavior::supportsGlobalSelection() returns
true, which it never does for windows or mac, as dcheng mentioned earlier:
https://code.google.com/p/chromium/codesearch#chromium/src/third_party/WebKit...

How about we rejig the ifdefs to something like:
#if defined(USE_X11) && !defined(OS_CHROMEOS)
  *result = ui::CLIPBOARD_TYPE_SELECTION;
  break;
#else
  // Chromeos and non-x11 unix builds don't support the X selection clipboard.
  return false;
#endif

     default:
-      NOTREACHED();
+      NOTIMPLEMENTED();
       return false;
   }
   return true;
 }
 
 }  // namespace content