Use a placeholder instead of the default plugin for missing plug-ins on Mac and Linux.

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 84d1cff5fbd0a6d204925d3f86921edcb64a0388..663379c5db92a89ebd95e6eb94137bae4069b39a 100644
--- a/chrome/common/render_messages.h
+++ b/chrome/common/render_messages.h
@@ -31,6 +31,7 @@
 #include "third_party/WebKit/Source/WebKit/chromium/public/WebCache.h"
 #include "third_party/WebKit/Source/WebKit/chromium/public/WebConsoleMessage.h"
 #include "ui/gfx/rect.h"
+#include "webkit/plugins/webplugininfo.h"
 
 // Singly-included section for enums and custom IPC traits.
 #ifndef CHROME_COMMON_RENDER_MESSAGES_H_
@@ -50,6 +51,16 @@ enum ViewHostMsg_JavaScriptStressTestControl_Commands {
   kJavaScriptStressTestPrepareStressRun = 1,
 };
 
+struct ChromeViewHostMsg_GetPluginInfo_Status {
+  // TODO(bauerb): Add more status values (blocked, click-to-play, out of date,
+  // requires authorization).
+  enum Value {
+    kAllowed,
+    kDisabled,
+    kNotFound,
+  };
+};
+
 namespace IPC {
 
 #if defined(OS_POSIX) && !defined(USE_AURA)
@@ -91,6 +102,7 @@ struct ParamTraits<ContentSettings> {
 
 #define IPC_MESSAGE_START ChromeMsgStart
 
+IPC_ENUM_TRAITS(ChromeViewHostMsg_GetPluginInfo_Status::Value)
 IPC_ENUM_TRAITS(InstantCompleteBehavior)
 IPC_ENUM_TRAITS(search_provider::OSDDType)
 IPC_ENUM_TRAITS(search_provider::InstallState)
@@ -127,6 +139,13 @@ IPC_STRUCT_TRAITS_BEGIN(WebKit::WebCache::UsageStats)
   IPC_STRUCT_TRAITS_MEMBER(deadSize)
 IPC_STRUCT_TRAITS_END()
 
+IPC_STRUCT_BEGIN(ChromeViewHostMsg_GetPluginInfo_Params)

[jam, 2011/09/30 17:01:21]

nit: we normally don't create structs unless we need > 4 parameters which is
what our IPC macros support. if you're just sending 3 out parameters, use
IPC_SYNC_MESSAGE_CONTROL4_3

[Bernhard Bauer, 2011/09/30 17:22:21]

I need to forward-declare the struct, and I can't do that for an enum. It looks
to me like including one of these _messages.h files in another *header* doesn't
work (because the missing include guards screw things up), so if I want to refer
to the message parameters in a header file, I have to forward-declare them :-/

[jam, 2011/09/30 17:40:19]

that's by design, since there's a lot of unnecessary template expansion when
they're included in headers
if you make ChromeRenderMessageFilter::PluginsLoaded() do all the work (and not
have GetPluginInfo()), then you don't need to forward declare this enum in a
header. the function except for the last two lines would only be indented once
more.

[Bernhard Bauer, 2011/10/05 13:34:33]

I split up ChromeViewHostMsg_GetPluginInfo_Params into its components. I kept
ChromeViewHostMsg_GetPluginInfo_Status for the forward-declaration (having a
nice signature for CRMF::GetPluginInfo makes it easier to unit-test it, for
example, and there are other instances of wrapping an enum in a struct, like
ViewMsg_StopFinding_Params).

+  IPC_STRUCT_MEMBER(ChromeViewHostMsg_GetPluginInfo_Status::Value, status)
+  IPC_STRUCT_MEMBER(webkit::WebPluginInfo, plugin)
+  IPC_STRUCT_MEMBER(std::string, actual_mime_type)
+IPC_STRUCT_END()
+
+
 //-----------------------------------------------------------------------------
 // RenderView messages
 // These are messages sent from the browser to the renderer process.
@@ -384,6 +403,17 @@ IPC_SYNC_MESSAGE_CONTROL2_1(ChromeViewHostMsg_GetPluginContentSetting,
                             std::string  /* resource */,
                             ContentSetting /* setting */)
 
+// Return information about a plugin for the given URL and MIME type.
+// 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_Params /* params */)
+
 // Specifies the URL as the first parameter (a wstring) and thumbnail as
 // binary data as the second parameter.
 IPC_MESSAGE_ROUTED3(ChromeViewHostMsg_Thumbnail,