Check whether the Pepper CDM is available before adding the key system.

chrome/common/render_messages.h

 // Copyright (c) 2012 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.
 
 // Multiply-included file, no traditional include guard.
 #include <map>
 #include <set>
 #include <string>
 #include <vector>
 
@@ skipping 485 matching lines @@
 // In contrast to ViewHostMsg_GetPluginInfo in content/, this IPC call knows
 // about specific reasons why a plug-in can't be used, for example because it's
 // disabled.
 IPC_SYNC_MESSAGE_CONTROL4_1(ChromeViewHostMsg_GetPluginInfo,
                             int /* render_view_id */,
                             GURL /* url */,
                             GURL /* top origin url */,
                             std::string /* mime_type */,
                             ChromeViewHostMsg_GetPluginInfo_Output /* output */)
 
+// Returns whether any plugin supporting |mime_type| is registered with Chrome.
+// Does not determine whether the plugin could actually be instantiated
+// (i.e. by checking Content Settings).
+IPC_SYNC_MESSAGE_CONTROL1_1(ChromeViewHostMsg_IsSupportingPluginAvailable,

[scherkus (not reviewing), 2013/09/11 22:34:41]

hmm... this name is a bit ambiguous but I'm having a hard time thinking of a
better alternative

WDYT about Plugin{Exists,Registered}WithMimeType? it conveys the mime-type-ness
and also that it's an existence check

[ddorwin, 2013/09/16 17:17:58]

Good suggestions. WDYT of IsPluginRegisteredForMimeType? I think that's exactly
what we're checking.

(I actually had to add "Pepper" due to the logic change.

+                           std::string /* mime_type */,

[scherkus (not reviewing), 2013/09/11 22:34:41]

indent is off

[ddorwin, 2013/09/16 17:17:58]

Done.

+                           bool /* available */)
+
 #if defined(ENABLE_PLUGIN_INSTALLATION)
 // Tells the browser to search for a plug-in that can handle the given MIME
 // type. The result will be sent asynchronously to the routing ID
 // |placeholder_id|.
 IPC_MESSAGE_ROUTED2(ChromeViewHostMsg_FindMissingPlugin,
                     int /* placeholder_id */,
                     std::string /* mime_type */)
 
 // Notifies the browser that a missing plug-in placeholder has been removed, so
 // the corresponding PluginPlaceholderHost can be deleted.
@@ skipping 231 matching lines @@
                     int /* page_id */,
                     bool /* supported */)
 
 // Tells listeners that a detailed message was reported to the console by
 // WebKit.
 IPC_MESSAGE_ROUTED4(ChromeViewHostMsg_DetailedConsoleMessageAdded,
                     string16 /* message */,
                     string16 /* source */,
                     extensions::StackTrace /* stack trace */,
                     int32 /* severity level */)