Distinguish plugin disconnections from plugin crashes.

content/common/view_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.
 
 // IPC messages for page rendering.
 // Multiply-included message file, hence no include guard.
 
 #include "base/process.h"
 #include "base/shared_memory.h"
 #include "base/string16.h"
@@ skipping 1984 matching lines @@
 IPC_MESSAGE_ROUTED0(ViewMsg_CancelDateTimeDialog)
 
 // WebKit and JavaScript error messages to log to the console
 // or debugger UI.
 IPC_MESSAGE_ROUTED4(ViewHostMsg_AddMessageToConsole,
                     int32, /* log level */
                     string16, /* msg */
                     int32, /* line number */
                     string16 /* source id */)
 
-// Sent by the renderer process to indicate that a plugin instance has
-// crashed.
-IPC_MESSAGE_ROUTED1(ViewHostMsg_CrashedPlugin,
-                    FilePath /* plugin_path */)
+// Sent by the renderer process to indicate that a plugin instance has crashed.
+// Note: |plugin_pid| should not be trusted. The corresponding process has
+// probably died. Moreover, the ID may have been reused by a new process. Any
+// usage other than displaying it in a prompt to the user is very likely to be
+// wrong.
+IPC_MESSAGE_ROUTED2(ViewHostMsg_CrashedPlugin,
+                    FilePath /* plugin_path */,
+                    base::ProcessId /* plugin_pid */)
 
 // Displays a box to confirm that the user wants to navigate away from the
 // page. Replies true if yes, false otherwise, the reply string is ignored,
 // but is included so that we can use OnJavaScriptMessageBoxClosed.
 IPC_SYNC_MESSAGE_ROUTED3_2(ViewHostMsg_RunBeforeUnloadConfirm,
                            GURL,     /* in - originating frame URL */
                            string16  /* in - alert message */,
                            bool      /* in - is a reload */,
                            bool      /* out - success */,
                            string16  /* out - This is ignored.*/)
@@ skipping 335 matching lines @@
                      int /* arb_robustness_status_code */)
 
 #if defined(OS_WIN)
 // Request that the given font characters be loaded by the browser so it's
 // cached by the OS. Please see RenderMessageFilter::OnPreCacheFontCharacters
 // for details.
 IPC_SYNC_MESSAGE_CONTROL2_0(ViewHostMsg_PreCacheFontCharacters,
                             LOGFONT /* font_data */,
                             string16 /* characters */)
 #endif