Back out r22981, it may have caused Windows test failures.

chrome/browser/plugin_process_host.cc

 // Copyright (c) 2009 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.
 
 #include "build/build_config.h"
 
 #include "chrome/browser/plugin_process_host.h"
 
 #if defined(OS_WIN)
 #include <windows.h>
@@ skipping 317 matching lines @@
                              const std::string& activex_clsid,
                              const std::wstring& locale) {
   info_ = info;
   set_name(info_.name);
 
   if (!CreateChannel())
     return false;
 
   // build command line for plugin, we have to quote the plugin's path to deal
   // with spaces.
-  std::wstring exe_path = GetChildPath();
-  if (exe_path.empty()) {
+  const CommandLine& browser_command_line = *CommandLine::ForCurrentProcess();
+  std::wstring exe_path =
+      browser_command_line.GetSwitchValue(switches::kBrowserSubprocessPath);
+  if (exe_path.empty() && !PathService::Get(base::FILE_EXE, &exe_path))
     return false;
-  }
 
   CommandLine cmd_line(exe_path);
   if (logging::DialogsAreSuppressed())
     cmd_line.AppendSwitch(switches::kNoErrorDialogs);
 
   // propagate the following switches to the plugin command line (along with
   // any associated values) if present in the browser command line
   static const wchar_t* const switch_names[] = {
     switches::kPluginStartupDialog,
     switches::kNoSandbox,
     switches::kSafePlugins,
     switches::kTestSandbox,
     switches::kUserAgent,
     switches::kDisableBreakpad,
     switches::kFullMemoryCrashReport,
     switches::kEnableLogging,
     switches::kDisableLogging,
     switches::kLoggingLevel,
     switches::kLogPluginMessages,
     switches::kUserDataDir,
     switches::kAllowAllActiveX,
     switches::kEnableDCHECK,
     switches::kSilentDumpOnDCHECK,
     switches::kMemoryProfiling,
     switches::kUseLowFragHeapCrt,
     switches::kEnableStatsTable,
   };
 
-  const CommandLine& browser_command_line = *CommandLine::ForCurrentProcess();
-
   for (size_t i = 0; i < arraysize(switch_names); ++i) {
     if (browser_command_line.HasSwitch(switch_names[i])) {
       cmd_line.AppendSwitchWithValue(
           switch_names[i],
           browser_command_line.GetSwitchValue(switch_names[i]));
     }
   }
 
   // If specified, prepend a launcher program to the command line.
   std::wstring plugin_launcher =
@@ skipping 241 matching lines @@
   DCHECK(MessageLoop::current() ==
          ChromeThread::GetMessageLoop(ChromeThread::IO));
 
   ChromePluginLib *chrome_plugin = ChromePluginLib::Find(info_.path);
   if (chrome_plugin) {
     void *data_ptr = const_cast<void*>(reinterpret_cast<const void*>(&data[0]));
     uint32 data_len = static_cast<uint32>(data.size());
     chrome_plugin->functions().on_message(data_ptr, data_len);
   }
 }