diff -r 000000000000 -r 6474c204b198 xpcom/build/BinaryPath.h
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/xpcom/build/BinaryPath.h	Wed Dec 31 06:09:35 2014 +0100
@@ -0,0 +1,156 @@
+/* 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/. */
+
+#ifndef mozilla_BinaryPath_h
+#define mozilla_BinaryPath_h
+
+#include "nsXPCOMPrivate.h" // for MAXPATHLEN
+#ifdef XP_WIN
+#include <windows.h>
+#elif defined(XP_MACOSX)
+#include <CoreFoundation/CoreFoundation.h>
+#elif defined(XP_UNIX)
+#include <sys/stat.h>
+#include <string.h>
+#endif
+
+namespace mozilla {
+
+class BinaryPath {
+public:
+#ifdef XP_WIN
+  static nsresult Get(const char *argv0, char aResult[MAXPATHLEN])
+  {
+    wchar_t wide_path[MAXPATHLEN];
+    nsresult rv = GetW(argv0, wide_path);
+    if (NS_FAILED(rv))
+      return rv;
+    WideCharToMultiByte(CP_UTF8, 0, wide_path, -1,
+                        aResult, MAXPATHLEN, nullptr, nullptr);
+    return NS_OK;
+  }
+
+private:
+  static nsresult GetW(const char *argv0, wchar_t aResult[MAXPATHLEN])
+  {
+    if (::GetModuleFileNameW(0, aResult, MAXPATHLEN))
+      return NS_OK;
+    return NS_ERROR_FAILURE;
+  }
+
+#elif defined(XP_MACOSX)
+  static nsresult Get(const char *argv0, char aResult[MAXPATHLEN])
+  {
+    // Works even if we're not bundled.
+    CFBundleRef appBundle = CFBundleGetMainBundle();
+    if (!appBundle)
+      return NS_ERROR_FAILURE;
+
+    CFURLRef executableURL = CFBundleCopyExecutableURL(appBundle);
+    if (!executableURL)
+      return NS_ERROR_FAILURE;
+
+    nsresult rv;
+    if (CFURLGetFileSystemRepresentation(executableURL, false, (UInt8 *)aResult, MAXPATHLEN))
+      rv = NS_OK;
+    else
+      rv = NS_ERROR_FAILURE;
+    CFRelease(executableURL);
+    return rv;
+  }
+
+#elif defined(ANDROID)
+  static nsresult Get(const char *argv0, char aResult[MAXPATHLEN])
+  {
+    // On Android, we use the GRE_HOME variable that is set by the Java
+    // bootstrap code.
+    const char *greHome = getenv("GRE_HOME");
+#if defined(MOZ_WIDGET_GONK)
+    if (!greHome)
+      greHome = "/system/b2g";
+#endif
+
+    if (!greHome)
+      return NS_ERROR_FAILURE;
+
+    snprintf(aResult, MAXPATHLEN, "%s/%s", greHome, "dummy");
+    aResult[MAXPATHLEN-1] = '\0';
+    return NS_OK;
+  }
+
+#elif defined(XP_UNIX)
+  static nsresult Get(const char *argv0, char aResult[MAXPATHLEN])
+  {
+    struct stat fileStat;
+    // on unix, there is no official way to get the path of the current binary.
+    // instead of using the MOZILLA_FIVE_HOME hack, which doesn't scale to
+    // multiple applications, we will try a series of techniques:
+    //
+    // 1) use realpath() on argv[0], which works unless we're loaded from the
+    //    PATH. Only do so if argv[0] looks like a path (contains a /).
+    // 2) manually walk through the PATH and look for ourself
+    // 3) give up
+    if (strchr(argv0, '/') && realpath(argv0, aResult) &&
+        stat(aResult, &fileStat) == 0)
+      return NS_OK;
+
+    const char *path = getenv("PATH");
+    if (!path)
+      return NS_ERROR_FAILURE;
+
+    char *pathdup = strdup(path);
+    if (!pathdup)
+      return NS_ERROR_OUT_OF_MEMORY;
+
+    bool found = false;
+    char *token = strtok(pathdup, ":");
+    while (token) {
+      char tmpPath[MAXPATHLEN];
+      sprintf(tmpPath, "%s/%s", token, argv0);
+      if (realpath(tmpPath, aResult) && stat(aResult, &fileStat) == 0) {
+        found = true;
+        break;
+      }
+      token = strtok(nullptr, ":");
+    }
+    free(pathdup);
+    if (found)
+      return NS_OK;
+    return NS_ERROR_FAILURE;
+  }
+
+#else
+#error Oops, you need platform-specific code here
+#endif
+
+public:
+  static nsresult GetFile(const char *argv0, nsIFile* *aResult)
+  {
+    nsCOMPtr<nsIFile> lf;
+#ifdef XP_WIN
+    wchar_t exePath[MAXPATHLEN];
+    nsresult rv = GetW(argv0, exePath);
+#else
+    char exePath[MAXPATHLEN];
+    nsresult rv = Get(argv0, exePath);
+#endif
+    if (NS_FAILED(rv))
+      return rv;
+#ifdef XP_WIN
+    rv = NS_NewLocalFile(nsDependentString(exePath), true,
+                         getter_AddRefs(lf));
+#else
+    rv = NS_NewNativeLocalFile(nsDependentCString(exePath), true,
+                               getter_AddRefs(lf));
+#endif
+    if (NS_FAILED(rv))
+      return rv;
+    NS_ADDREF(*aResult = lf);
+    return NS_OK;
+  }
+};
+
+}
+
+#endif /* mozilla_BinaryPath_h */