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

chrome/common/render_messages.h

Index: chrome/common/render_messages.h
diff --git a/chrome/common/render_messages.h b/chrome/common/render_messages.h
index bf9b30f0b8ab81ad78b66bd34c61d576e90d9f2d..bd5b93b138e90ca6dc220718c5994e469b588604 100644
--- a/chrome/common/render_messages.h
+++ b/chrome/common/render_messages.h
@@ -503,6 +503,13 @@ IPC_SYNC_MESSAGE_CONTROL4_1(ChromeViewHostMsg_GetPluginInfo,
                             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