diff -r 000000000000 -r 6474c204b198 toolkit/xre/nsX11ErrorHandler.cpp
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/toolkit/xre/nsX11ErrorHandler.cpp	Wed Dec 31 06:09:35 2014 +0100
@@ -0,0 +1,172 @@
+/* -*- Mode: C++; tab-width: 40; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#include "nsX11ErrorHandler.h"
+
+#include "prenv.h"
+#include "nsXULAppAPI.h"
+#include "nsExceptionHandler.h"
+#include "nsDebug.h"
+
+#include "mozilla/X11Util.h"
+#include <X11/Xlib.h>
+
+#define BUFSIZE 2048 // What Xlib uses with XGetErrorDatabaseText
+
+extern "C" {
+static int
+X11Error(Display *display, XErrorEvent *event) {
+  // Get an indication of how long ago the request that caused the error was
+  // made.
+  unsigned long age = NextRequest(display) - event->serial;
+
+  // Get a string to represent the request that caused the error.
+  nsAutoCString message;
+  if (event->request_code < 128) {
+    // Core protocol request
+    message.AppendInt(event->request_code);
+  } else {
+    // Extension request
+
+    // man XSetErrorHandler says "the error handler should not call any
+    // functions (directly or indirectly) on the display that will generate
+    // protocol requests or that will look for input events" so we use another
+    // temporary Display to request extension information.  This assumes on
+    // the DISPLAY environment variable has been set and matches what was used
+    // to open |display|.
+    Display *tmpDisplay = XOpenDisplay(nullptr);
+    if (tmpDisplay) {
+      int nExts;
+      char** extNames = XListExtensions(tmpDisplay, &nExts);
+      int first_error;
+      if (extNames) {
+        for (int i = 0; i < nExts; ++i) {
+          int major_opcode, first_event;
+          if (XQueryExtension(tmpDisplay, extNames[i],
+                              &major_opcode, &first_event, &first_error)
+              && major_opcode == event->request_code) {
+            message.Append(extNames[i]);
+            message.Append('.');
+            message.AppendInt(event->minor_code);
+            break;
+          }
+        }
+
+        XFreeExtensionList(extNames);
+      }
+      XCloseDisplay(tmpDisplay);
+
+#if (MOZ_WIDGET_GTK == 2)
+      // GDK2 calls XCloseDevice the devices that it opened on startup, but
+      // the XI protocol no longer ensures that the devices will still exist.
+      // If they have been removed, then a BadDevice error results.  Ignore
+      // this error.
+      if (message.EqualsLiteral("XInputExtension.4") &&
+          event->error_code == first_error + 0) {
+        return 0;
+      }
+#endif
+    }
+  }
+
+  char buffer[BUFSIZE];
+  if (message.IsEmpty()) {
+    buffer[0] = '\0';
+  } else {
+    XGetErrorDatabaseText(display, "XRequest", message.get(), "",
+                          buffer, sizeof(buffer));
+  }
+
+  nsAutoCString notes;
+  if (buffer[0]) {
+    notes.Append(buffer);
+  } else {
+    notes.Append("Request ");
+    notes.AppendInt(event->request_code);
+    notes.Append('.');
+    notes.AppendInt(event->minor_code);
+  }
+
+  notes.Append(": ");
+
+  // Get a string to describe the error.
+  XGetErrorText(display, event->error_code, buffer, sizeof(buffer));
+  notes.Append(buffer);
+
+  // For requests where Xlib gets the reply synchronously, |age| will be 1
+  // and the stack will include the function making the request.  For
+  // asynchronous requests, the current stack will often be unrelated to the
+  // point of making the request, even if |age| is 1, but sometimes this may
+  // help us count back to the point of the request.  With XSynchronize on,
+  // the stack will include the function making the request, even though
+  // |age| will be 2 for asynchronous requests because XSynchronize is
+  // implemented by an empty request from an XSync, which has not yet been
+  // processed.
+  if (age > 1) {
+    // XSynchronize returns the previous "after function".  If a second
+    // XSynchronize call returns the same function after an enable call then
+    // synchronization must have already been enabled.
+    if (XSynchronize(display, True) == XSynchronize(display, False)) {
+      notes.Append("; sync");
+    } else {
+      notes.Append("; ");
+      notes.AppendInt(uint32_t(age));
+      notes.Append(" requests ago");
+    }
+  }
+
+#ifdef MOZ_CRASHREPORTER
+  switch (XRE_GetProcessType()) {
+  case GeckoProcessType_Default:
+  case GeckoProcessType_Plugin:
+  case GeckoProcessType_Content:
+    CrashReporter::AppendAppNotesToCrashReport(notes);
+    break;
+  default: 
+    ; // crash report notes not supported.
+  }
+#endif
+
+#ifdef DEBUG
+  // The resource id is unlikely to be useful in a crash report without
+  // context of other ids, but add it to the debug console output.
+  notes.Append("; id=0x");
+  notes.AppendInt(uint32_t(event->resourceid), 16);
+#ifdef MOZ_X11
+  // Actually, for requests where Xlib gets the reply synchronously,
+  // MOZ_X_SYNC=1 will not be necessary, but we don't have a table to tell us
+  // which requests get a synchronous reply.
+  if (!PR_GetEnv("MOZ_X_SYNC")) {
+    notes.Append("\nRe-running with MOZ_X_SYNC=1 in the environment may give a more helpful backtrace.");
+  }
+#endif
+#endif
+
+#ifdef MOZ_WIDGET_QT
+  // We should not abort here if MOZ_X_SYNC is not set
+  // until http://bugreports.qt.nokia.com/browse/QTBUG-4042
+  // not fixed, just print error value
+  if (!PR_GetEnv("MOZ_X_SYNC")) {
+    fprintf(stderr, "XError: %s\n", notes.get());
+    return 0; // temporary workaround for bug 161472
+  }
+#endif
+
+  NS_RUNTIMEABORT(notes.get());
+  return 0; // not reached
+}
+}
+
+void
+InstallX11ErrorHandler()
+{
+  XSetErrorHandler(X11Error);
+
+  Display *display = mozilla::DefaultXDisplay();
+  NS_ASSERTION(display, "No X display");
+  if (PR_GetEnv("MOZ_X_SYNC")) {
+    XSynchronize(display, True);
+  }
+}